core: Refactor the wait code utilizing the new fdtable.

* src/fdtable.c, src/fdtable.h: Largely extend.
* src/wait-global.c, src/wait-private.c, src/wait-user.c: Remove and
move code to ...
* src/wait.c: here.
(_gpgme_fd_table_init, fd_table_put): Remove.  Do not call them.
(_gpgme_add_io_cb, _gpgme_add_io_cb_user): Change to use the fdtable.
(_gpgme_remove_io_cb, _gpgme_remove_io_cb_user):  Ditto.
(_gpgme_wait_global_event_cb):  Ditto.
(gpgme_wait_ext, _gpgme_wait_on_condition): Ditto.
* src/wait.h (struct io_cb_tag_s): Add fields 'serial' and 'desc'.
Change 'idx' to 'fd'.
(struct fd_table): Remove.
* src/context.h (struct gpgme_context): Remoce 'fdt'.  Rename io_cbs
to user_io_cbs for clarity.
* src/engine-gpgsm.c: Unify trace output.
(start): Pass a description along with the IO handlers.
* src/priv-io.h (struct io_select_fd_s): Rename to io_select_s.
(io_select_t): New.
* src/gpgme.c (_gpgme_cancel_with_err): Replace arg 'ctx' by 'serial'.
(gpgme_cancel): Adjust.
--

This is the second part of a larger refactoring of the wait/event
code.  Does currently only work on Unix and with the private wait
functions (i.e. the async operations don't yet work).

Signed-off-by: Werner Koch <[email protected]>

15 files changed, 992 insertions, 939 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 79028a17..781441cc 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -75,7 +75,7 @@ main_sources =								\
 	data-compat.c data-identify.c					\
 	signers.c sig-notation.c					\
         fdtable.c fdtable.h                                             \
-	wait.c wait-global.c wait-private.c wait-user.c wait.h		\
+	wait.c wait.h	                                          	\
 	op-support.c							\
 	encrypt.c encrypt-sign.c decrypt.c decrypt-verify.c verify.c	\
 	sign.c passphrase.c progress.c					\
diff --git a/src/context.h b/src/context.h
index 7333d2d5..4142b684 100644
--- a/src/context.h
+++ b/src/context.h
@@ -194,10 +194,8 @@ struct gpgme_context
   gpgme_status_cb_t status_cb;
   void *status_cb_value;
 
-  /* A list of file descriptors in active use by the current
-     operation.  */
-  struct fd_table fdt;
-  struct gpgme_io_cbs io_cbs;
+  /* User specific I/O callbacks.  */
+  struct gpgme_io_cbs user_io_cbs;
 };
 
 
@@ -208,7 +206,7 @@ struct gpgme_context
 
 gpg_error_t _gpgme_get_ctx (uint64_t serial, gpgme_ctx_t *r_ctx);
 
-gpgme_error_t _gpgme_cancel_with_err (gpgme_ctx_t ctx, gpg_error_t ctx_err,
+gpgme_error_t _gpgme_cancel_with_err (uint64_t serial, gpg_error_t ctx_err,
                                       gpg_error_t op_err);
 
 
diff --git a/src/engine-gpgsm.c b/src/engine-gpgsm.c
index 9ecdbe47..086ed32d 100644
--- a/src/engine-gpgsm.c
+++ b/src/engine-gpgsm.c
@@ -910,7 +910,7 @@ status_handler (void *opaque, int fd)
 	  /* Try our best to terminate the connection friendly.  */
 	  /*	  assuan_write_line (gpgsm->assuan_ctx, "BYE"); */
           TRACE (DEBUG_CTX, "gpgme:status_handler", gpgsm,
-		  "fd 0x%x: error from assuan (%d) getting status line : %s",
+		  "fd=%d: error from assuan (%d) getting status line : %s",
                   fd, err, gpg_strerror (err));
 	}
       else if (linelen >= 3
@@ -922,7 +922,7 @@ status_handler (void *opaque, int fd)
 	  if (! err)
 	    err = gpg_error (GPG_ERR_GENERAL);
           TRACE (DEBUG_CTX, "gpgme:status_handler", gpgsm,
-		  "fd 0x%x: ERR line - mapped to: %s",
+		  "fd=%d: ERR line - mapped to: %s",
                   fd, err ? gpg_strerror (err) : "ok");
 	  /* Try our best to terminate the connection friendly.  */
 	  /*	  assuan_write_line (gpgsm->assuan_ctx, "BYE"); */
@@ -951,7 +951,7 @@ status_handler (void *opaque, int fd)
               err = gpgsm->colon.fnc (gpgsm->colon.fnc_value, NULL);
             }
           TRACE (DEBUG_CTX, "gpgme:status_handler", gpgsm,
-		  "fd 0x%x: OK line - final status: %s",
+		  "fd=%d: OK line - final status: %s",
                   fd, err ? gpg_strerror (err) : "ok");
 	  _gpgme_io_close (gpgsm->status_cb.fd);
 	  return err;
@@ -1026,7 +1026,7 @@ status_handler (void *opaque, int fd)
 		}
 	    }
           TRACE (DEBUG_CTX, "gpgme:status_handler", gpgsm,
-		  "fd 0x%x: D line; final status: %s",
+		  "fd=%d: D line; final status: %s",
                   fd, err? gpg_strerror (err):"ok");
         }
       else if (linelen > 2
@@ -1068,7 +1068,7 @@ status_handler (void *opaque, int fd)
             }
 
           TRACE (DEBUG_CTX, "gpgme:status_handler", gpgsm,
-		  "fd 0x%x: D inlinedata; final status: %s",
+		  "fd=%d: D inlinedata; final status: %s",
                   fd, err? gpg_strerror (err):"ok");
         }
       else if (linelen > 2
@@ -1106,7 +1106,7 @@ status_handler (void *opaque, int fd)
 	  else
 	    fprintf (stderr, "[UNKNOWN STATUS]%s %s", line + 2, rest);
           TRACE (DEBUG_CTX, "gpgme:status_handler", gpgsm,
-		  "fd 0x%x: S line (%s) - final status: %s",
+		  "fd=%d: S line (%s) - final status: %s",
                   fd, line+2, err? gpg_strerror (err):"ok");
 	}
       else if (linelen >= 7
@@ -1131,12 +1131,14 @@ status_handler (void *opaque, int fd)
 
 
 static gpgme_error_t
-add_io_cb (engine_gpgsm_t gpgsm, iocb_data_t *iocbd, gpgme_io_cb_t handler)
+add_io_cb (engine_gpgsm_t gpgsm, iocb_data_t *iocbd, gpgme_io_cb_t handler,
+           const char *handler_desc)
 {
   gpgme_error_t err;
 
-  TRACE_BEG  (DEBUG_ENGINE, "engine-gpgsm:add_io_cb", gpgsm,
-              "fd=%d, dir %d", iocbd->fd, iocbd->dir);
+  TRACE_BEG  (DEBUG_ENGINE, "engine-gpgsm:add_io_cb", NULL,
+              "fd=%d, dir %d (%s-handler)",
+              iocbd->fd, iocbd->dir, handler_desc);
   err = (*gpgsm->io_cbs.add) (gpgsm->io_cbs.add_priv,
 			      iocbd->fd, iocbd->dir,
 			      handler, iocbd->data, &iocbd->tag);
@@ -1205,15 +1207,19 @@ start (engine_gpgsm_t gpgsm, const char *command)
       return gpg_error (GPG_ERR_GENERAL);
     }
 
-  err = add_io_cb (gpgsm, &gpgsm->status_cb, status_handler);
+  err = add_io_cb (gpgsm, &gpgsm->status_cb, status_handler, "status");
   if (!err && gpgsm->input_cb.fd != -1)
-    err = add_io_cb (gpgsm, &gpgsm->input_cb, _gpgme_data_outbound_handler);
+    err = add_io_cb (gpgsm, &gpgsm->input_cb,
+                     _gpgme_data_outbound_handler, "outbound");
   if (!err && gpgsm->output_cb.fd != -1)
-    err = add_io_cb (gpgsm, &gpgsm->output_cb, _gpgme_data_inbound_handler);
+    err = add_io_cb (gpgsm, &gpgsm->output_cb,
+                     _gpgme_data_inbound_handler, "inbound");
   if (!err && gpgsm->message_cb.fd != -1)
-    err = add_io_cb (gpgsm, &gpgsm->message_cb, _gpgme_data_outbound_handler);
+    err = add_io_cb (gpgsm, &gpgsm->message_cb,
+                     _gpgme_data_outbound_handler, "outbound");
   if (!err && gpgsm->diag_cb.fd != -1)
-    err = add_io_cb (gpgsm, &gpgsm->diag_cb, _gpgme_data_inbound_handler);
+    err = add_io_cb (gpgsm, &gpgsm->diag_cb,
+                     _gpgme_data_inbound_handler, "inbound");
 
   if (!err)
     err = assuan_write_line (gpgsm->assuan_ctx, command);
diff --git a/src/fdtable.c b/src/fdtable.c
index 2e682dea..de240fc3 100644
--- a/src/fdtable.c
+++ b/src/fdtable.c
@@ -37,6 +37,41 @@ struct fdtable_item_s
 {
   int fd;  /* -1 indicates an unused entry.  */
 
+  uint64_t owner;  /* The S/N of the context owning this FD.  */
+
+  /* ACTIVE is set if this fd is in the global event loop, has an
+   * active callback (.io_cb), and has seen the start event. */
+  unsigned int active:1;
+  /* DONE is set if this fd was previously active but is not active
+   * any longer, either because is finished successfully or its I/O
+   * callback returned an error.  Note that ACTIVE and DONE should
+   * never both be set. */
+  unsigned int done:1;
+
+  /* Infos for io_select.  */
+  unsigned int for_read:1;
+  unsigned int for_write:1;
+  unsigned int signaled:1;
+
+  /* We are in a closing handler.  Note that while this flag is active
+   * the remove code holds an index into the table.  Thus we better
+   * make sure that the index won't change.  Or change the removal
+   * code to re-find the fd.  */
+  unsigned int closing:1;
+
+  /* We are currently running the IO callback. */
+  unsigned int io_cb_running:1;
+
+  /* The I/O callback handler with its value context. */
+  struct {
+    gpgme_io_cb_t cb;
+    void *value;
+  } io_cb;
+
+  /* The error code and the operational error for the done status.  */
+  gpg_error_t done_status;
+  gpg_error_t done_op_err;
+
   /* The callback to be called before the descriptor is actually closed.  */
   struct {
     fdtable_handler_t handler;
@@ -109,6 +144,16 @@ _gpgme_fdtable_insert (int fd)
     idx = firstunused;
 
   fdtable[idx].fd = fd;
+  fdtable[idx].owner = 0;
+  fdtable[idx].active = 0;
+  fdtable[idx].done = 0;
+  fdtable[idx].for_read = 0;
+  fdtable[idx].for_write = 0;
+  fdtable[idx].signaled = 0;
+  fdtable[idx].closing = 0;
+  fdtable[idx].io_cb_running = 0;
+  fdtable[idx].io_cb.cb = NULL;
+  fdtable[idx].io_cb.value = NULL;
   fdtable[idx].close_notify.handler = NULL;
   fdtable[idx].close_notify.value   = NULL;
   err = 0;
@@ -161,6 +206,178 @@ _gpgme_fdtable_add_close_notify (int fd,
 }
 
 
+/* Set the I/O callback for the FD.  FD must already exist otherwise
+ * GPG_ERR_NO_KEY is returned.  OWNER is the serial of the owning
+ * context.  If DIRECTION is 1 the callback wants to read from it; if
+ * it is 0 the callback want to write to it.  CB is the actual
+ * callback and CB_VALUE the values passed to that callback.  If a
+ * callback as already been set GPG_ERR_DUP_VALUE is returned.  To
+ * remove the handler, FD and OWNER must be passed as usual but CB be
+ * passed as NULL.
+ */
+gpg_error_t
+_gpgme_fdtable_set_io_cb (int fd, uint64_t owner, int direction,
+                          gpgme_io_cb_t cb, void *cb_value)
+{
+  gpg_error_t err;
+  int idx;
+
+  TRACE_BEG  (DEBUG_SYSIO, __func__, NULL, "fd=%d ctx=%lu dir=%d",
+              fd, (unsigned long)owner, direction);
+
+  if (fd < 0 || !owner)
+    return TRACE_ERR (gpg_error (GPG_ERR_INV_ARG));
+
+  LOCK (fdtable_lock);
+
+  if (cb)
+    {
+      for (idx=0; idx < fdtablesize; idx++)
+        if (fdtable[idx].fd == fd)
+          break;
+      if (idx == fdtablesize)
+        {
+          err = gpg_error (GPG_ERR_NO_KEY);
+          TRACE_LOG ("with_cb: fd=%d owner=%lu", fd, (unsigned long)owner);
+          goto leave;
+        }
+
+      if (fdtable[idx].io_cb.cb)
+        {
+          err = gpg_error (GPG_ERR_DUP_VALUE);
+          goto leave;
+        }
+
+      fdtable[idx].owner = owner;
+
+      fdtable[idx].for_read = (direction == 1);
+      fdtable[idx].for_write = (direction == 0);
+      fdtable[idx].signaled = 0;
+
+      fdtable[idx].io_cb.cb = cb;
+      fdtable[idx].io_cb.value = cb_value;
+    }
+  else  /* Remove.  */
+    {
+      /* We compare also the owner as a cross-check.  */
+      for (idx=0; idx < fdtablesize; idx++)
+        if (fdtable[idx].fd == fd && fdtable[idx].owner == owner)
+          break;
+      if (idx == fdtablesize)
+        {
+          err = gpg_error (GPG_ERR_NO_KEY);
+          TRACE_LOG ("remove: fd=%d owner=%lu", fd, (unsigned long)owner);
+          for (idx=0; idx < fdtablesize; idx++)
+            TRACE_LOG ("  TBL: fd=%d owner=%lu", fdtable[idx].fd, (unsigned long)fdtable[idx].owner);
+          goto leave;
+        }
+
+      fdtable[idx].for_read = 0;
+      fdtable[idx].for_write = 0;
+      fdtable[idx].signaled = 0;
+
+      fdtable[idx].io_cb.cb = NULL;
+      fdtable[idx].io_cb.value = NULL;
+      fdtable[idx].owner = 0;
+    }
+  err = 0;
+
+ leave:
+  UNLOCK (fdtable_lock);
+  return TRACE_ERR (err);
+}
+
+
+/* Set all FDs of OWNER into the active state.  */
+gpg_error_t
+_gpgme_fdtable_set_active (uint64_t owner)
+{
+  int idx;
+
+  TRACE_BEG  (DEBUG_SYSIO, __func__, NULL, "ctx=%lu", (unsigned long)owner);
+
+  if (!owner )
+    return TRACE_ERR (gpg_error (GPG_ERR_INV_ARG));
+
+  LOCK (fdtable_lock);
+
+  for (idx=0; idx < fdtablesize; idx++)
+    if (fdtable[idx].fd != -1 && fdtable[idx].owner == owner
+        && fdtable[idx].io_cb.cb)
+      {
+        fdtable[idx].active = 1;
+        fdtable[idx].done   = 0;
+      }
+
+  UNLOCK (fdtable_lock);
+  return TRACE_ERR (0);
+}
+
+
+/* Set all FDs of OWNER into the done state.  STATUS and OP_ERR are
+ * recorded. */
+gpg_error_t
+_gpgme_fdtable_set_done (uint64_t owner, gpg_error_t status, gpg_error_t op_err)
+{
+  int idx;
+
+  TRACE_BEG  (DEBUG_SYSIO, __func__, NULL, "ctx=%lu", (unsigned long)owner);
+
+  if (!owner )
+    return TRACE_ERR (gpg_error (GPG_ERR_INV_ARG));
+
+  LOCK (fdtable_lock);
+
+  for (idx=0; idx < fdtablesize; idx++)
+    if (fdtable[idx].fd != -1 && fdtable[idx].owner == owner
+        && fdtable[idx].active)
+      {
+        fdtable[idx].active = 0;
+        fdtable[idx].done   = 1;
+        fdtable[idx].done_status = status;
+        fdtable[idx].done_op_err = op_err;
+      }
+
+  UNLOCK (fdtable_lock);
+  return TRACE_ERR (0);
+}
+
+
+/* Walk over all fds in FDS and copy the signaled flag if set.  It
+ * does not clear any signal flag in the global table.  */
+void
+_gpgme_fdtable_set_signaled (io_select_t fds, unsigned int nfds)
+{
+  int idx;
+  unsigned int n, count;
+
+  if (!nfds)
+    return;
+
+  /* FIXME: Highly inefficient code in case of large select lists.  */
+  count = 0;
+  LOCK (fdtable_lock);
+  for (idx=0; idx < fdtablesize; idx++)
+    {
+      if (fdtable[idx].fd == -1)
+        continue;
+      for (n = 0; n < nfds; n++)
+        if (fdtable[idx].fd == fds[n].fd)
+          {
+            if (fds[n].signaled && !fdtable[idx].signaled)
+              {
+                fdtable[idx].signaled = 1;
+                count++; /* Only for tracing.  */
+              }
+            break;
+          }
+    }
+  UNLOCK (fdtable_lock);
+
+  TRACE  (DEBUG_SYSIO, __func__, NULL, "fds newly signaled=%u", count);
+}
+
+
 /* Remove FD from the table after calling the close handler.  Note
  * that at the time the close handler is called the FD has been
  * removed form the table.  Thus the close handler may not access the
@@ -191,15 +408,273 @@ _gpgme_fdtable_remove (int fd)
       return TRACE_ERR (gpg_error (GPG_ERR_NO_KEY));
     }
 
+  TRACE_LOG ("removal of fd=%d owner=%lu (closing=%d)",
+             fdtable[idx].fd, (unsigned long)fdtable[idx].owner,
+             fdtable[idx].closing);
+
   handler = fdtable[idx].close_notify.handler;
   fdtable[idx].close_notify.handler = NULL;
   handlervalue = fdtable[idx].close_notify.value;
   fdtable[idx].close_notify.value = NULL;
-  fdtable[idx].fd = -1;
+
+  /* The handler might call into the fdtable again, so of we have a
+   * handler we can't immediately close it but instead record the fact
+   * and remove the entry from the table only after the handler has
+   * been run.  */
+  if (handler)
+    fdtable[idx].closing = 1;
+  else if (!fdtable[idx].closing)
+    fdtable[idx].fd = -1;
 
   UNLOCK (fdtable_lock);
 
-  err = handler? handler (fd, handlervalue) : 0;
+  if (handler)
+    {
+      err = handler (fd, handlervalue);
+      LOCK (fdtable_lock);
+      TRACE_LOG ("final removal of fd=%d owner=%lu (closing=%d)",
+                 fdtable[idx].fd, (unsigned long)fdtable[idx].owner,
+                 fdtable[idx].closing);
+      fdtable[idx].fd = -1;
+      UNLOCK (fdtable_lock);
+    }
+  else
+    err = 0;
 
   return TRACE_ERR (err);
 }
+
+
+/* Return the number of active I/O callbacks for OWNER or for all if
+ * OWNER is 0.  */
+unsigned int
+_gpgme_fdtable_io_cb_count (uint64_t owner)
+{
+  int idx;
+  unsigned int count = 0;
+
+  LOCK (fdtable_lock);
+  for (idx=0; idx < fdtablesize; idx++)
+    if (fdtable[idx].fd != -1 && (!owner || fdtable[idx].owner == owner))
+      count++;
+  UNLOCK (fdtable_lock);
+
+  TRACE  (DEBUG_SYSIO, __func__, NULL, "ctx=%lu count=%u",
+          (unsigned long)owner, count);
+  return count;
+}
+
+
+/* Run all signaled IO callbacks of OWNER or all signaled callbacks if
+ * OWNER is 0.  Returns an error code on the first real error
+ * encountered.  If R_OP_ERR is not NULL an optional operational error
+ * can be stored tehre.  For EOF the respective flags are set.  */
+gpg_error_t
+_gpgme_fdtable_run_io_cbs (uint64_t owner, gpg_error_t *r_op_err)
+{
+  gpg_error_t err;
+  int idx;
+  int fd;
+  gpgme_io_cb_t iocb;
+  struct io_cb_data iocb_data;
+  uint64_t serial;
+  unsigned int cb_count;
+  gpgme_ctx_t actx;
+
+  if (r_op_err)
+    *r_op_err = 0;
+
+  TRACE_BEG  (DEBUG_SYSIO, __func__, NULL, "ctx=%lu", owner);
+
+  for (;;)
+    {
+      fd = -1;
+      LOCK (fdtable_lock);
+      for (idx=0; idx < fdtablesize; idx++)
+        if (fdtable[idx].fd != -1 && (!owner || fdtable[idx].owner == owner)
+            && fdtable[idx].signaled)
+          {
+            fd = fdtable[idx].fd;
+            serial = fdtable[idx].owner;
+            iocb = fdtable[idx].io_cb.cb;
+            iocb_data.handler_value = fdtable[idx].io_cb.value;
+            iocb_data.op_err = 0;
+            fdtable[idx].signaled = 0;
+            if (iocb)
+              {
+                fdtable[idx].io_cb_running = 1;
+                break;
+              }
+          }
+      UNLOCK (fdtable_lock);
+      if (fd == -1)
+        break;  /* No more callbacks found.  */
+
+      /* If the context object is still valid and has not been
+       * canceled, we run the I/O callback.  */
+      err = _gpgme_get_ctx (serial, &actx);
+      if (!err)
+        {
+          err = iocb (&iocb_data, fd);
+          if (err)
+            TRACE_LOG ("iocb(fd=%d) err=%s", fd, gpg_strerror (err));
+        }
+
+      /* Clear the running flag and while we are at it also count the
+       * remaining callbacks.  */
+      cb_count = 0;
+      LOCK (fdtable_lock);
+      for (idx=0; idx < fdtablesize; idx++)
+        {
+          if (fdtable[idx].fd == -1)
+            continue;
+          if (fdtable[idx].fd == fd)
+            fdtable[idx].io_cb_running = 0;
+          if (fdtable[idx].owner == serial)
+            cb_count++;
+        }
+      UNLOCK (fdtable_lock);
+
+      /* Handle errors or success from the IO callback.  In the error
+       * case we close all fds belonging to the same context.  In the
+       * success case we check whether any callback is left and only
+       * if that is not the case, tell the engine that we are done.
+       * The latter indirectly sets the fd into the done state.  */
+      if (err)
+        {
+          _gpgme_cancel_with_err (serial, err, 0);
+          return TRACE_ERR (err);
+        }
+      else if (iocb_data.op_err)
+        {
+          /* An operational error occurred.  Cancel the current
+           * operation but not the session, and signal it.  */
+          _gpgme_cancel_with_err (serial, 0, iocb_data.op_err);
+
+          /* NOTE: This relies on the operational error being
+           * generated after the operation really has completed, for
+           * example after no further status line output is generated.
+           * Otherwise the following I/O will spill over into the next
+           * operation. */
+          if (r_op_err)
+            *r_op_err = iocb_data.op_err;
+          return TRACE_ERR (0);
+        }
+      else if (!cb_count && actx)
+        {
+          struct gpgme_io_event_done_data data = { 0, 0 };
+          _gpgme_engine_io_event (actx->engine, GPGME_EVENT_DONE, &data);
+        }
+    }
+
+  return TRACE_ERR (0);
+}
+
+
+/* Retrieve a list of file descriptors owned by OWNER, or with OWNER
+ * being 0 of all fds, and store that list as a new array at R_FDS.
+ * Return the number of FDS in that list or 0 if none were selected.
+ * FLAGS give further selection flags:
+ *   FDTABLE_FLAG_ACTIVE       - Only those with the active flag set.
+ *   FDTABLE_FLAG_DONE         - Only those with the done flag set.
+ *   FDTABLE_FLAG_FOR_READ     - Only those with the readable FDs.
+ *   FDTABLE_FLAG_FOR_WRITE    - Only those with the writable FDs.
+ *   FDTABLE_FLAG_SIGNALED     - Only those with the signaled flag set.
+ *   FDTABLE_FLAG_NOT_SIGNALED - Only those with the signaled flag cleared.
+ *   FDTABLE_FLAG_CLEAR        - Clear the signaled flag..
+ */
+unsigned int
+_gpgme_fdtable_get_fds (io_select_t *r_fds, uint64_t owner, unsigned int flags)
+{
+  int idx;
+  unsigned int count = 0;
+  io_select_t fds;
+
+  *r_fds = NULL;
+  gpg_err_set_errno (0);
+  /* We take an easy approach and allocate the array at the size of
+   * the entire fdtable.  */
+  fds = calloc (fdtablesize, sizeof *fds);
+  if (!fds)
+    return 0;
+
+  LOCK (fdtable_lock);
+  for (idx=0; idx < fdtablesize; idx++)
+    if (fdtable[idx].fd != -1 && (!owner || fdtable[idx].owner == owner))
+      {
+        if ((flags & FDTABLE_FLAG_ACTIVE) && !fdtable[idx].active)
+          continue;
+        if ((flags & FDTABLE_FLAG_DONE) && !fdtable[idx].done)
+          continue;
+        if ((flags & FDTABLE_FLAG_FOR_READ) && !fdtable[idx].for_read)
+          continue;
+        if ((flags & FDTABLE_FLAG_FOR_WRITE) && !fdtable[idx].for_write)
+          continue;
+        if ((flags & FDTABLE_FLAG_SIGNALED) && !fdtable[idx].signaled)
+          continue;
+        if ((flags & FDTABLE_FLAG_NOT_SIGNALED) && fdtable[idx].signaled)
+          continue;
+
+        if (fdtable[idx].io_cb_running || fdtable[idx].closing)
+          continue; /* The callback has not yet finished or we are
+                     * already closing.  Does not make sense to allow
+                     * selecting on it.  */
+
+        fds[count].fd = fdtable[idx].fd;
+        fds[count].for_read = fdtable[idx].for_read;
+        fds[count].for_write = fdtable[idx].for_write;
+        fds[count].signaled =
+          (flags & FDTABLE_FLAG_SIGNALED)? 0 : fdtable[idx].signaled;
+
+        count++;
+      }
+
+  UNLOCK (fdtable_lock);
+  *r_fds = fds;
+
+  TRACE  (DEBUG_SYSIO, __func__, NULL, "ctx=%lu count=%u",
+          (unsigned long)owner, count);
+  return count;
+}
+
+
+/* If OWNER is 0 return the status info of the first fd with the done
+ * flag set.  If OWNER is not 0 search for a matching owner with the
+ * done flag set and return its status info.  Returns the serial
+ * number of the context found.  */
+uint64_t
+_gpgme_fdtable_get_done (uint64_t owner,
+                         gpg_error_t *r_status, gpg_error_t *r_op_err)
+{
+  uint64_t serial = 0;
+  int idx;
+
+  TRACE_BEG (DEBUG_SYSIO, __func__, NULL, "ctx=%lu", (unsigned long)owner);
+
+  LOCK (fdtable_lock);
+
+  for (idx=0; idx < fdtablesize; idx++)
+    if (fdtable[idx].fd != -1 && (!owner || fdtable[idx].owner == owner)
+        && fdtable[idx].done)
+      {
+        /* Found.  If an owner has been given also clear the done
+         * flags from all other fds of this owner.  Note that they
+         * have the same status info anyway.  */
+        *r_status = fdtable[idx].done_status;
+        *r_op_err = fdtable[idx].done_op_err;
+        fdtable[idx].done = 0;
+        serial = fdtable[idx].owner;
+        if (owner)
+          {
+            for (; idx < fdtablesize; idx++)
+              if (fdtable[idx].fd != -1 && fdtable[idx].owner == owner)
+                fdtable[idx].done = 0;
+          }
+        break;
+      }
+
+  UNLOCK (fdtable_lock);
+
+  TRACE_SUC ("ctx=%lu", (unsigned long)serial);
+  return serial;
+}
diff --git a/src/fdtable.h b/src/fdtable.h
index 6038b249..6f621849 100644
--- a/src/fdtable.h
+++ b/src/fdtable.h
@@ -21,6 +21,18 @@
 #ifndef GPGME_FDTABLE_H
 #define GPGME_FDTABLE_H
 
+#include "priv-io.h"
+
+/* Flags used by _gpgme_fdtable_get_fds.  */
+#define FDTABLE_FLAG_ACTIVE    1  /* Only those with the active flag set.   */
+#define FDTABLE_FLAG_DONE      2  /* Only those with the done flag set      */
+#define FDTABLE_FLAG_FOR_READ  4  /* Only those with the signaled flag set. */
+#define FDTABLE_FLAG_FOR_WRITE 8  /* Only those with the for_read flag set. */
+#define FDTABLE_FLAG_SIGNALED 16  /* Only those with the signaled flag set. */
+#define FDTABLE_FLAG_NOT_SIGNALED 32  /* Ditto reversed.                    */
+#define FDTABLE_FLAG_CLEAR   128  /* Clear the signaled flag.               */
+
+
 /* The handler type associated with an FD.  It is called with the FD
  * and the registered pointer.  The handler may return an error code
  * but there is no guarantee that this code is used; in particular
@@ -35,9 +47,35 @@ gpg_error_t _gpgme_fdtable_insert (int fd);
 gpg_error_t _gpgme_fdtable_add_close_notify (int fd,
                                              fdtable_handler_t handler,
                                              void *value);
+/* Set or remove the I/O callback.  */
+gpg_error_t _gpgme_fdtable_set_io_cb (int fd, uint64_t owner, int direction,
+                                      gpgme_io_cb_t cb, void *cb_value);
+
+/* Set all FDs of OWNER into the active state.  */
+gpg_error_t _gpgme_fdtable_set_active (uint64_t owner);
+
+/* Set all FDs of OWNER into the done state.  */
+gpg_error_t _gpgme_fdtable_set_done (uint64_t owner,
+                                     gpg_error_t status, gpg_error_t op_err);
+
+/* Walk over all FDS and copy the signaled flag if set.  */
+void _gpgme_fdtable_set_signaled (io_select_t fds, unsigned int nfds);
 
 /* Remove FD from the table.  This also runs the close handlers.  */
 gpg_error_t _gpgme_fdtable_remove (int fd);
 
+/* Return the number of active I/O callbacks for OWNER.  */
+unsigned int _gpgme_fdtable_io_cb_count (uint64_t owner);
+
+/* Run all the signaled IO callbacks of OWNER.  */
+gpg_error_t _gpgme_fdtable_run_io_cbs (uint64_t owner, gpg_error_t *r_op_err);
+
+/* Return a list of FDs matching the OWNER and FLAGS.  */
+unsigned int _gpgme_fdtable_get_fds (io_select_t *r_fds,
+                                     uint64_t owner, unsigned int flags);
+
+/* Return the status info for the entry of OWNER.  */
+uint64_t _gpgme_fdtable_get_done (uint64_t owner, gpg_error_t *r_status,
+                                  gpg_error_t *r_op_err);
 
 #endif /*GPGME_FDTABLE_H*/
diff --git a/src/gpgme.c b/src/gpgme.c
index 283290f4..19489023 100644
--- a/src/gpgme.c
+++ b/src/gpgme.c
@@ -135,7 +135,6 @@ gpgme_new (gpgme_ctx_t *r_ctx)
   ctx->include_certs = GPGME_INCLUDE_CERTS_DEFAULT;
   ctx->protocol = GPGME_PROTOCOL_OpenPGP;
   ctx->sub_protocol = GPGME_PROTOCOL_DEFAULT;
-  _gpgme_fd_table_init (&ctx->fdt);
 
   LOCK (context_list_lock);
   if (def_lc_ctype)
@@ -218,36 +217,43 @@ _gpgme_get_ctx (uint64_t serial, gpgme_ctx_t *r_ctx)
     *r_ctx = ctx;
   return err;
 }
+
+
+
+/* Cancel the context indetified with SERIAL.  Pass CTX_ERR or OP_ERR
+ * down to the engine.  */
 gpgme_error_t
-_gpgme_cancel_with_err (gpgme_ctx_t ctx, gpg_error_t ctx_err,
+_gpgme_cancel_with_err (uint64_t serial, gpg_error_t ctx_err,
 			gpg_error_t op_err)
 {
   gpgme_error_t err;
+  gpgme_ctx_t ctx;
   struct gpgme_io_event_done_data data;
 
   TRACE_BEG  (DEBUG_CTX, "_gpgme_cancel_with_err", NULL,
               "ctx=%lu ctx_err=%i op_err=%i",
-	      CTXSERIAL (ctx), ctx_err, op_err);
+	      (unsigned long)serial, ctx_err, op_err);
 
-  if (ctx_err)
-    {
-      err = _gpgme_engine_cancel (ctx->engine);
-      if (err)
-	return TRACE_ERR (err);
-    }
+  LOCK (context_list_lock);
+  for (ctx = context_list; ctx; ctx = ctx->next_ctx)
+    if (ctx->serial == serial)
+      break;
+  UNLOCK (context_list_lock);
+
+  if (!ctx)
+    err = gpg_error (GPG_ERR_NO_OBJ);
+  else if (ctx_err)
+    err = _gpgme_engine_cancel (ctx->engine);
   else
+    err = _gpgme_engine_cancel_op (ctx->engine);
+
+  if (!err)
     {
-      err = _gpgme_engine_cancel_op (ctx->engine);
-      if (err)
-	return TRACE_ERR (err);
+      data.err = ctx_err;
+      data.op_err = op_err;
+      _gpgme_engine_io_event (ctx->engine, GPGME_EVENT_DONE, &data);
     }
-
-  data.err = ctx_err;
-  data.op_err = op_err;
-
-  _gpgme_engine_io_event (ctx->engine, GPGME_EVENT_DONE, &data);
-
-  return TRACE_ERR (0);
+  return TRACE_ERR (err);
 }
 
 
@@ -262,7 +268,7 @@ gpgme_cancel (gpgme_ctx_t ctx)
   if (!ctx)
     return TRACE_ERR (gpg_error (GPG_ERR_INV_VALUE));
 
-  err = _gpgme_cancel_with_err (ctx, gpg_error (GPG_ERR_CANCELED), 0);
+  err = _gpgme_cancel_with_err (ctx->serial, gpg_error (GPG_ERR_CANCELED), 0);
 
   return TRACE_ERR (err);
 }
@@ -317,7 +323,7 @@ gpgme_release (gpgme_ctx_t ctx)
 
   _gpgme_engine_release (ctx->engine);
   ctx->engine = NULL;
-  _gpgme_fd_table_deinit (&ctx->fdt);
+  /* FIXME: Remove stale FDs belonging to us? */
   _gpgme_release_result (ctx);
   _gpgme_signers_clear (ctx);
   _gpgme_sig_notation_clear (ctx);
@@ -972,17 +978,17 @@ gpgme_set_io_cbs (gpgme_ctx_t ctx, gpgme_io_cbs_t io_cbs)
              CTXSERIAL (ctx),
              io_cbs, io_cbs->add, io_cbs->add_priv, io_cbs->remove,
              io_cbs->event, io_cbs->event_priv);
-      ctx->io_cbs = *io_cbs;
+      ctx->user_io_cbs = *io_cbs;
     }
   else
     {
       TRACE (DEBUG_CTX, "gpgme_set_io_cbs", NULL,
              "ctx=%lu io_cbs=%p (default)", CTXSERIAL (ctx), io_cbs);
-      ctx->io_cbs.add = NULL;
-      ctx->io_cbs.add_priv = NULL;
-      ctx->io_cbs.remove = NULL;
-      ctx->io_cbs.event = NULL;
-      ctx->io_cbs.event_priv = NULL;
+      ctx->user_io_cbs.add = NULL;
+      ctx->user_io_cbs.add_priv = NULL;
+      ctx->user_io_cbs.remove = NULL;
+      ctx->user_io_cbs.event = NULL;
+      ctx->user_io_cbs.event_priv = NULL;
     }
 }
 
@@ -1054,7 +1060,7 @@ gpgme_get_io_cbs (gpgme_ctx_t ctx, gpgme_io_cbs_t io_cbs)
          io_cbs, io_cbs->add, io_cbs->add_priv, io_cbs->remove,
          io_cbs->event, io_cbs->event_priv);
 
-  *io_cbs = ctx->io_cbs;
+  *io_cbs = ctx->user_io_cbs;
 }
 
 
diff --git a/src/op-support.c b/src/op-support.c
index 6affb5e4..874827e1 100644
--- a/src/op-support.c
+++ b/src/op-support.c
@@ -173,7 +173,7 @@ _gpgme_op_reset (gpgme_ctx_t ctx, int type)
 	return err;
     }
 
-  if (type == 1 || (type == 2 && !ctx->io_cbs.add))
+  if (type == 1 || (type == 2 && !ctx->user_io_cbs.add))
     {
       /* Use private event loop.  */
       io_cbs.add = _gpgme_add_io_cb;
@@ -182,7 +182,7 @@ _gpgme_op_reset (gpgme_ctx_t ctx, int type)
       io_cbs.event = _gpgme_wait_private_event_cb;
       io_cbs.event_priv = ctx;
     }
-  else if (! ctx->io_cbs.add)
+  else if (!ctx->user_io_cbs.add)
     {
       /* Use global event loop.  */
       io_cbs.add = _gpgme_add_io_cb;
@@ -194,9 +194,9 @@ _gpgme_op_reset (gpgme_ctx_t ctx, int type)
   else
     {
       /* Use user event loop.  */
-      io_cbs.add = _gpgme_wait_user_add_io_cb;
+      io_cbs.add = _gpgme_add_io_cb_user;
       io_cbs.add_priv = ctx;
-      io_cbs.remove = _gpgme_wait_user_remove_io_cb;
+      io_cbs.remove = _gpgme_remove_io_cb_user;
       io_cbs.event = _gpgme_wait_user_event_cb;
       io_cbs.event_priv = ctx;
     }
diff --git a/src/posix-io.c b/src/posix-io.c
index b754ac34..5d9edf10 100644
--- a/src/posix-io.c
+++ b/src/posix-io.c
@@ -622,10 +622,14 @@ _gpgme_io_spawn (const char *path, char *const argv[], unsigned int flags,
 }
 
 
-/* Select on the list of fds.  Returns: -1 = error, 0 = timeout or
-   nothing to select, > 0 = number of signaled fds.  */
+/* Select on the list of fds.
+ *
+ * Returns:  -1 = error,
+ *            0 = timeout or nothing to select,
+ *          > 0 = number of signaled fds.
+ */
 int
-_gpgme_io_select (struct io_select_fd_s *fds, size_t nfds, int nonblock)
+_gpgme_io_select (io_select_t fds, unsigned int nfds, int nonblock)
 {
   fd_set readfds;
   fd_set writefds;
@@ -638,7 +642,7 @@ _gpgme_io_select (struct io_select_fd_s *fds, size_t nfds, int nonblock)
   struct timeval timeout = { 1, 0 };
   void *dbg_help = NULL;
   TRACE_BEG  (DEBUG_SYSIO, "_gpgme_io_select", NULL,
-	      "nfds=%zu, nonblock=%u", nfds, nonblock);
+	      "nfds=%u, nonblock=%u", nfds, nonblock);
 
   FD_ZERO (&readfds);
   FD_ZERO (&writefds);
@@ -736,6 +740,7 @@ _gpgme_io_select (struct io_select_fd_s *fds, size_t nfds, int nonblock)
   return TRACE_SYSRES (count);
 }
 
+
 
 int
 _gpgme_io_recvmsg (int fd, struct msghdr *msg, int flags)
diff --git a/src/priv-io.h b/src/priv-io.h
index f40cdffc..27cc07eb 100644
--- a/src/priv-io.h
+++ b/src/priv-io.h
@@ -51,14 +51,15 @@ struct spawn_fd_item_s
   int arg_loc;
 };
 
-struct io_select_fd_s
+struct io_select_s
 {
   int fd;
-  int for_read;
-  int for_write;
-  int signaled;
-  void *opaque;
+  unsigned int for_read:1;
+  unsigned int for_write:1;
+  unsigned int signaled:1;
 };
+typedef struct io_select_s *io_select_t;
+
 
 /* These function are either defined in posix-io.c or w32-io.c.  */
 void _gpgme_io_subsystem_init (void);
@@ -89,7 +90,7 @@ int _gpgme_io_spawn (const char *path, char *const argv[], unsigned int flags,
 		     void (*atfork) (void *opaque, int reserved),
 		     void *atforkvalue, pid_t *r_pid);
 
-int _gpgme_io_select (struct io_select_fd_s *fds, size_t nfds, int nonblock);
+int _gpgme_io_select (io_select_t fds, unsigned int nfds, int nonblock);
 
 /* Write the printable version of FD to the buffer BUF of length
    BUFLEN.  The printable version is the representation on the command
diff --git a/src/verify.c b/src/verify.c
index 8aa9d281..f6bc23c4 100644
--- a/src/verify.c
+++ b/src/verify.c
@@ -911,7 +911,7 @@ parse_error (gpgme_signature_t sig, char *args, int set_status)
       && gpg_err_code (err) == GPG_ERR_BAD_DATA)
     {
       /* This indicates a double plaintext.  The only solid way to
-         handle this is by failing the oepration.  */
+         handle this is by failing the operation.  */
       return gpg_error (GPG_ERR_BAD_DATA);
     }
   else if (!set_status)
diff --git a/src/wait-global.c b/src/wait-global.c
deleted file mode 100644
index e88962e0..00000000
--- a/src/wait-global.c
+++ /dev/null
@@ -1,401 +0,0 @@
-/* wait-global.c
- * Copyright (C) 2000 Werner Koch (dd9jn)
- * Copyright (C) 2001, 2002, 2003, 2004, 2005 g10 Code GmbH
- *
- * This file is part of GPGME.
- *
- * GPGME is free software; you can redistribute it and/or modify it
- * under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation; either version 2.1 of
- * the License, or (at your option) any later version.
- *
- * GPGME is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this program; if not, see <https://gnu.org/licenses/>.
- * SPDX-License-Identifier: LGPL-2.1-or-later
- */
-
-#if HAVE_CONFIG_H
-#include <config.h>
-#endif
-#include <stdlib.h>
-#include <assert.h>
-#include <string.h>
-#include <errno.h>
-
-#include "gpgme.h"
-#include "sema.h"
-#include "util.h"
-#include "context.h"
-#include "wait.h"
-#include "priv-io.h"
-#include "ops.h"
-#include "debug.h"
-
-/* The global event loop is used for all asynchronous operations
-   (except key listing) for which no user I/O callbacks are specified.
-
-   A context sets up its initial I/O callbacks and then sends the
-   GPGME_EVENT_START event.  After that, it is added to the global
-   list of active contexts.
-
-   The gpgme_wait function contains a select() loop over all file
-   descriptors in all active contexts.  If an error occurs, it closes
-   all fds in that context and moves the context to the global done
-   list.  Likewise, if a context has removed all I/O callbacks, it is
-   moved to the global done list.
-
-   All contexts in the global done list are eligible for being
-   returned by gpgme_wait if requested by the caller.  */
-
-/* The ctx_list_lock protects the list of active and done contexts.
-   Insertion into any of these lists is only allowed when the lock is
-   held.  This allows a muli-threaded program to loop over gpgme_wait
-   and in parallel start asynchronous gpgme operations.
-
-   However, the fd tables in the contexts are not protected by this
-   lock.  They are only allowed to change either before the context is
-   added to the active list (ie, before the start event is signalled)
-   or in a callback handler.  */
-DEFINE_STATIC_LOCK (ctx_list_lock);
-
-/* A ctx_list_item is an item in the global list of active or done
-   contexts.  */
-struct ctx_list_item
-{
-  /* Every ctx_list_item is an element in a doubly linked list.  The
-     list pointers are protected by the ctx_list_lock.  */
-  struct ctx_list_item *next;
-  struct ctx_list_item *prev;
-
-  gpgme_ctx_t ctx;
-  /* The status is set when the ctx is moved to the done list.  */
-  gpgme_error_t status;
-  gpgme_error_t op_err;
-};
-
-/* The active list contains all contexts that are in the global event
-   loop, have active I/O callbacks, and have already seen the start
-   event.  */
-static struct ctx_list_item *ctx_active_list;
-
-/* The done list contains all contexts that have previously been
-   active but now are not active any longer, either because they
-   finished successfully or an I/O callback returned an error.  The
-   status field in the list item contains the error value (or 0 if
-   successful).  */
-static struct ctx_list_item *ctx_done_list;
-
-
-/* Enter the context CTX into the active list.  */
-static gpgme_error_t
-ctx_active (gpgme_ctx_t ctx)
-{
-  struct ctx_list_item *li = malloc (sizeof (struct ctx_list_item));
-  if (!li)
-    return gpg_error_from_syserror ();
-  li->ctx = ctx;
-
-  LOCK (ctx_list_lock);
-  /* Add LI to active list.  */
-  li->next = ctx_active_list;
-  li->prev = NULL;
-  if (ctx_active_list)
-    ctx_active_list->prev = li;
-  ctx_active_list = li;
-  UNLOCK (ctx_list_lock);
-  return 0;
-}
-
-
-/* Enter the context CTX into the done list with status STATUS.  */
-static void
-ctx_done (gpgme_ctx_t ctx, gpgme_error_t status, gpgme_error_t op_err)
-{
-  struct ctx_list_item *li;
-
-  LOCK (ctx_list_lock);
-  li = ctx_active_list;
-  while (li && li->ctx != ctx)
-    li = li->next;
-  assert (li);
-
-  /* Remove LI from active list.  */
-  if (li->next)
-    li->next->prev = li->prev;
-  if (li->prev)
-    li->prev->next = li->next;
-  else
-    ctx_active_list = li->next;
-
-  li->status = status;
-  li->op_err = op_err;
-
-  /* Add LI to done list.  */
-  li->next = ctx_done_list;
-  li->prev = NULL;
-  if (ctx_done_list)
-    ctx_done_list->prev = li;
-  ctx_done_list = li;
-  UNLOCK (ctx_list_lock);
-}
-
-
-/* Find finished context CTX (or any context if CTX is NULL) and
-   return its status in STATUS after removing it from the done list.
-   If a matching context could be found, return it.  Return NULL if no
-   context could be found.  */
-static gpgme_ctx_t
-ctx_wait (gpgme_ctx_t ctx, gpgme_error_t *status, gpgme_error_t *op_err)
-{
-  struct ctx_list_item *li;
-
-  LOCK (ctx_list_lock);
-  li = ctx_done_list;
-  if (ctx)
-    {
-      /* A specific context is requested.  */
-      while (li && li->ctx != ctx)
-	li = li->next;
-    }
-  if (li)
-    {
-      ctx = li->ctx;
-      if (status)
-	*status = li->status;
-      if (op_err)
-	*op_err = li->op_err;
-
-      /* Remove LI from done list.  */
-      if (li->next)
-	li->next->prev = li->prev;
-      if (li->prev)
-	li->prev->next = li->next;
-      else
-	ctx_done_list = li->next;
-      free (li);
-    }
-  else
-    ctx = NULL;
-  UNLOCK (ctx_list_lock);
-  return ctx;
-}
-
-
-/* Internal I/O callback functions.  */
-
-/* The add_io_cb and remove_io_cb handlers are shared with the private
-   event loops.  */
-
-void
-_gpgme_wait_global_event_cb (void *data, gpgme_event_io_t type,
-			     void *type_data)
-{
-  gpgme_ctx_t ctx = (gpgme_ctx_t) data;
-
-  assert (ctx);
-
-  switch (type)
-    {
-    case GPGME_EVENT_START:
-      {
-	gpgme_error_t err = ctx_active (ctx);
-
-	if (err)
-	  /* An error occurred.  Close all fds in this context, and
-	     send the error in a done event.  */
-	  _gpgme_cancel_with_err (ctx, err, 0);
-      }
-      break;
-
-    case GPGME_EVENT_DONE:
-      {
-	gpgme_io_event_done_data_t done_data =
-	  (gpgme_io_event_done_data_t) type_data;
-
-	ctx_done (ctx, done_data->err, done_data->op_err);
-      }
-      break;
-
-    case GPGME_EVENT_NEXT_KEY:
-      assert (!"Unexpected event GPGME_EVENT_NEXT_KEY");
-      break;
-
-    case GPGME_EVENT_NEXT_TRUSTITEM:
-      assert (!"Unexpected event GPGME_EVENT_NEXT_TRUSTITEM");
-      break;
-
-    default:
-      assert (!"Unexpected event");
-      break;
-    }
-}
-
-
-
-/* Perform asynchronous operations in the global event loop (ie, any
-   asynchronous operation except key listing and trustitem listing
-   operations).  If CTX is not a null pointer, the function will
-   return if the asynchronous operation in the context CTX finished.
-   Otherwise the function will return if any asynchronous operation
-   finished.  If HANG is zero, the function will not block for a long
-   time.  Otherwise the function does not return until an operation
-   matching CTX finished.
-
-   If a matching context finished, it is returned, and *STATUS is set
-   to the error value of the operation in that context.  Otherwise, if
-   the timeout expires, NULL is returned and *STATUS is 0.  If an
-   error occurs, NULL is returned and *STATUS is set to the error
-   value.  */
-gpgme_ctx_t
-gpgme_wait_ext (gpgme_ctx_t ctx, gpgme_error_t *status,
-		gpgme_error_t *op_err, int hang)
-{
-  do
-    {
-      unsigned int i = 0;
-      struct ctx_list_item *li;
-      struct fd_table fdt;
-      int nr;
-
-      /* Collect the active file descriptors.  */
-      LOCK (ctx_list_lock);
-      for (li = ctx_active_list; li; li = li->next)
-	i += li->ctx->fdt.size;
-      fdt.fds = malloc (i * sizeof (struct io_select_fd_s));
-      if (!fdt.fds)
-	{
-          int saved_err = gpg_error_from_syserror ();
-	  UNLOCK (ctx_list_lock);
-	  if (status)
-	    *status = saved_err;
-	  if (op_err)
-	    *op_err = 0;
-	  return NULL;
-	}
-      fdt.size = i;
-      i = 0;
-      for (li = ctx_active_list; li; li = li->next)
-	{
-	  memcpy (&fdt.fds[i], li->ctx->fdt.fds,
-		  li->ctx->fdt.size * sizeof (struct io_select_fd_s));
-	  i += li->ctx->fdt.size;
-	}
-      UNLOCK (ctx_list_lock);
-
-      nr = _gpgme_io_select (fdt.fds, fdt.size, 0);
-      if (nr < 0)
-	{
-          int saved_err = gpg_error_from_syserror ();
-	  free (fdt.fds);
-	  if (status)
-	    *status = saved_err;
-	  if (op_err)
-	    *op_err = 0;
-	  return NULL;
-	}
-
-      for (i = 0; i < fdt.size && nr; i++)
-	{
-	  if (fdt.fds[i].fd != -1 && fdt.fds[i].signaled)
-	    {
-	      gpgme_ctx_t ictx;
-	      gpgme_error_t err = 0;
-	      gpgme_error_t local_op_err = 0;
-	      struct wait_item_s *item;
-
-	      assert (nr);
-	      nr--;
-
-	      item = (struct wait_item_s *) fdt.fds[i].opaque;
-	      assert (item);
-	      ictx = item->ctx;
-	      assert (ictx);
-
-	      LOCK (ctx->lock);
-	      if (ctx->canceled)
-		err = gpg_error (GPG_ERR_CANCELED);
-	      UNLOCK (ctx->lock);
-
-	      if (!err)
-		err = _gpgme_run_io_cb (&fdt.fds[i], 0, &local_op_err);
-	      if (err || local_op_err)
-		{
-		  /* An error occurred.  Close all fds in this context,
-		     and signal it.  */
-		  _gpgme_cancel_with_err (ictx, err, local_op_err);
-
-		  /* Break out of the loop, and retry the select()
-		     from scratch, because now all fds should be
-		     gone.  */
-		  break;
-		}
-	    }
-	}
-      free (fdt.fds);
-
-      /* Now some contexts might have finished successfully.  */
-      LOCK (ctx_list_lock);
-    retry:
-      for (li = ctx_active_list; li; li = li->next)
-	{
-	  gpgme_ctx_t actx = li->ctx;
-
-	  for (i = 0; i < actx->fdt.size; i++)
-	    if (actx->fdt.fds[i].fd != -1)
-	      break;
-	  if (i == actx->fdt.size)
-	    {
-	      struct gpgme_io_event_done_data data;
-	      data.err = 0;
-	      data.op_err = 0;
-
-	      /* FIXME: This does not perform too well.  We have to
-		 release the lock because the I/O event handler
-		 acquires it to remove the context from the active
-		 list.  Two alternative strategies are worth
-		 considering: Either implement the DONE event handler
-		 here in a lock-free manner, or save a list of all
-		 contexts to be released and call the DONE events
-		 afterwards.  */
-	      UNLOCK (ctx_list_lock);
-	      _gpgme_engine_io_event (actx->engine, GPGME_EVENT_DONE, &data);
-	      LOCK (ctx_list_lock);
-	      goto retry;
-	    }
-	}
-      UNLOCK (ctx_list_lock);
-
-      {
-	gpgme_ctx_t dctx = ctx_wait (ctx, status, op_err);
-
-	if (dctx)
-	  {
-	    ctx = dctx;
-	    hang = 0;
-	  }
-	else if (!hang)
-	  {
-	    ctx = NULL;
-	    if (status)
-	      *status = 0;
-	    if (op_err)
-	      *op_err = 0;
-	  }
-      }
-    }
-  while (hang);
-
-  return ctx;
-}
-
-
-gpgme_ctx_t
-gpgme_wait (gpgme_ctx_t ctx, gpgme_error_t *status, int hang)
-{
-  return gpgme_wait_ext (ctx, status, NULL, hang);
-}
diff --git a/src/wait-private.c b/src/wait-private.c
deleted file mode 100644
index 417cb2b3..00000000
--- a/src/wait-private.c
+++ /dev/null
@@ -1,180 +0,0 @@
-/* wait-private.c
- * Copyright (C) 2000 Werner Koch (dd9jn)
- * Copyright (C) 2001, 2002, 2003, 2004, 2005 g10 Code GmbH
- *
- * This file is part of GPGME.
- *
- * GPGME is free software; you can redistribute it and/or modify it
- * under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation; either version 2.1 of
- * the License, or (at your option) any later version.
- *
- * GPGME is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this program; if not, see <https://gnu.org/licenses/>.
- * SPDX-License-Identifier: LGPL-2.1-or-later
- */
-
-#if HAVE_CONFIG_H
-#include <config.h>
-#endif
-#include <assert.h>
-#include <errno.h>
-
-#include "gpgme.h"
-#include "context.h"
-#include "wait.h"
-#include "ops.h"
-#include "priv-io.h"
-#include "util.h"
-#include "debug.h"
-
-
-/* The private event loops are used for all blocking operations, and
-   for the key and trust item listing operations.  They are completely
-   separated from each other.  */
-
-
-/* Internal I/O callback functions.  */
-
-/* The add_io_cb and remove_io_cb handlers are shared with the global
-   event loops.  */
-
-void
-_gpgme_wait_private_event_cb (void *data, gpgme_event_io_t type,
-			      void *type_data)
-{
-  switch (type)
-    {
-    case GPGME_EVENT_START:
-      /* Nothing to do here, as the wait routine is called after the
-	 initialization is finished.  */
-      break;
-
-    case GPGME_EVENT_DONE:
-      break;
-
-    case GPGME_EVENT_NEXT_KEY:
-      _gpgme_op_keylist_event_cb (data, type, type_data);
-      break;
-
-    case GPGME_EVENT_NEXT_TRUSTITEM:
-      _gpgme_op_trustlist_event_cb (data, type, type_data);
-      break;
-    }
-}
-
-
-/* If COND is a null pointer, wait until the blocking operation in CTX
-   finished and return its error value.  Otherwise, wait until COND is
-   satisfied or the operation finished.  */
-gpgme_error_t
-_gpgme_wait_on_condition (gpgme_ctx_t ctx, volatile int *cond,
-			  gpgme_error_t *op_err_p)
-{
-  gpgme_error_t err = 0;
-  int hang = 1;
-
-  if (op_err_p)
-    *op_err_p = 0;
-
-  do
-    {
-      int nr = _gpgme_io_select (ctx->fdt.fds, ctx->fdt.size, 0);
-      unsigned int i;
-
-      if (nr < 0)
-	{
-	  /* An error occurred.  Close all fds in this context, and
-	     signal it.  */
-	  err = gpg_error_from_syserror ();
-          _gpgme_cancel_with_err (ctx, err, 0);
-
-	  return err;
-	}
-
-      for (i = 0; i < ctx->fdt.size && nr; i++)
-	{
-	  if (ctx->fdt.fds[i].fd != -1 && ctx->fdt.fds[i].signaled)
-	    {
-	      gpgme_error_t op_err = 0;
-
-	      ctx->fdt.fds[i].signaled = 0;
-	      assert (nr);
-	      nr--;
-
-	      LOCK (ctx->lock);
-	      if (ctx->canceled)
-		err = gpg_error (GPG_ERR_CANCELED);
-	      UNLOCK (ctx->lock);
-
-	      if (!err)
-		err = _gpgme_run_io_cb (&ctx->fdt.fds[i], 0, &op_err);
-	      if (err)
-		{
-		  /* An error occurred.  Close all fds in this context,
-		     and signal it.  */
-		  _gpgme_cancel_with_err (ctx, err, 0);
-
-		  return err;
-		}
-	      else if (op_err)
-		{
-		  /* An operational error occurred.  Cancel the current
-		     operation but not the session, and signal it.  */
-		  _gpgme_cancel_with_err (ctx, 0, op_err);
-
-		  /* NOTE: This relies on the operational error being
-		     generated after the operation really has
-		     completed, for example after no further status
-		     line output is generated.  Otherwise the
-		     following I/O will spill over into the next
-		     operation.  */
-		  if (op_err_p)
-		    *op_err_p = op_err;
-		  return 0;
-		}
-	    }
-	}
-
-      for (i = 0; i < ctx->fdt.size; i++)
-	if (ctx->fdt.fds[i].fd != -1)
-	  break;
-      if (i == ctx->fdt.size)
-	{
-	  struct gpgme_io_event_done_data data;
-	  data.err = 0;
-	  data.op_err = 0;
-	  _gpgme_engine_io_event (ctx->engine, GPGME_EVENT_DONE, &data);
-	  hang = 0;
-	}
-      if (cond && *cond)
-	hang = 0;
-    }
-  while (hang);
-
-  return 0;
-}
-
-
-/* Wait until the blocking operation in context CTX has finished and
-   return the error value.  This variant can not be used for
-   session-based protocols.  */
-gpgme_error_t
-_gpgme_wait_one (gpgme_ctx_t ctx)
-{
-  return _gpgme_wait_on_condition (ctx, NULL, NULL);
-}
-
-/* Wait until the blocking operation in context CTX has finished and
-   return the error value.  This is the right variant to use for
-   sesion-based protocols.  */
-gpgme_error_t
-_gpgme_wait_one_ext (gpgme_ctx_t ctx, gpgme_error_t *op_err)
-{
-  return _gpgme_wait_on_condition (ctx, NULL, op_err);
-}
diff --git a/src/wait-user.c b/src/wait-user.c
deleted file mode 100644
index 2a42170c..00000000
--- a/src/wait-user.c
+++ /dev/null
@@ -1,133 +0,0 @@
-/* wait-user.c
- * Copyright (C) 2000 Werner Koch (dd9jn)
- * Copyright (C) 2001, 2002, 2003, 2004, 2005 g10 Code GmbH
- *
- * This file is part of GPGME.
- *
- * GPGME is free software; you can redistribute it and/or modify it
- * under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation; either version 2.1 of
- * the License, or (at your option) any later version.
- *
- * GPGME is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this program; if not, see <https://gnu.org/licenses/>.
- * SPDX-License-Identifier: LGPL-2.1-or-later
- */
-
-#if HAVE_CONFIG_H
-#include <config.h>
-#endif
-#include <assert.h>
-
-#include "gpgme.h"
-#include "context.h"
-#include "priv-io.h"
-#include "wait.h"
-#include "ops.h"
-#include "debug.h"
-
-
-/* The user event loops are used for all asynchronous operations for
-   which a user callback is defined.  */
-
-
-/* Internal I/O Callbacks.  */
-
-gpgme_error_t
-_gpgme_user_io_cb_handler (void *data, int fd)
-{
-  gpgme_error_t err = 0;
-  gpgme_error_t op_err = 0;
-  struct tag *tag = (struct tag *) data;
-  gpgme_ctx_t ctx;
-
-  (void)fd;
-
-  assert (data);
-  ctx = tag->ctx;
-  assert (ctx);
-
-  LOCK (ctx->lock);
-  if (ctx->canceled)
-    err = gpg_error (GPG_ERR_CANCELED);
-  UNLOCK (ctx->lock);
-
-  if (! err)
-    err = _gpgme_run_io_cb (&ctx->fdt.fds[tag->idx], 0, &op_err);
-  if (err || op_err)
-    _gpgme_cancel_with_err (ctx, err, op_err);
-  else
-    {
-      unsigned int i;
-
-      for (i = 0; i < ctx->fdt.size; i++)
-	if (ctx->fdt.fds[i].fd != -1)
-	  break;
-
-      if (i == ctx->fdt.size)
-	{
-	  struct gpgme_io_event_done_data done_data;
-
-	  done_data.err = 0;
-	  done_data.op_err = 0;
-	  _gpgme_engine_io_event (ctx->engine, GPGME_EVENT_DONE, &done_data);
-	}
-    }
-  return 0;
-}
-
-
-/* Register the file descriptor FD with the handler FNC (which gets
-   FNC_DATA as its first argument) for the direction DIR.  DATA should
-   be the context for which the fd is added.  R_TAG will hold the tag
-   that can be used to remove the fd.  */
-gpgme_error_t
-_gpgme_wait_user_add_io_cb (void *data, int fd, int dir, gpgme_io_cb_t fnc,
-			    void *fnc_data, void **r_tag)
-{
-  gpgme_ctx_t ctx = (gpgme_ctx_t) data;
-  struct tag *tag;
-  gpgme_error_t err;
-
-  assert (ctx);
-  err = _gpgme_add_io_cb (data, fd, dir, fnc, fnc_data, r_tag);
-  if (err)
-    return err;
-  tag = *r_tag;
-  assert (tag);
-  err = (*ctx->io_cbs.add) (ctx->io_cbs.add_priv, fd, dir,
-			    _gpgme_user_io_cb_handler, *r_tag,
-			    &tag->user_tag);
-  if (err)
-    _gpgme_remove_io_cb (*r_tag);
-  return err;
-}
-
-
-void
-_gpgme_wait_user_remove_io_cb (void *data)
-{
-  struct tag *tag = (struct tag *) data;
-  gpgme_ctx_t ctx;
-
-  assert (tag);
-  ctx = tag->ctx;
-
-  (*ctx->io_cbs.remove) (tag->user_tag);
-  _gpgme_remove_io_cb (data);
-}
-
-
-void
-_gpgme_wait_user_event_cb (void *data, gpgme_event_io_t type, void *type_data)
-{
-  gpgme_ctx_t ctx = data;
-
-  if (ctx->io_cbs.event)
-    (*ctx->io_cbs.event) (ctx->io_cbs.event_priv, type, type_data);
-}
diff --git a/src/wait.c b/src/wait.c
index 52eb6f4d..7418f00d 100644
--- a/src/wait.c
+++ b/src/wait.c
@@ -38,190 +38,440 @@
 #include "priv-io.h"
 #include "engine.h"
 #include "debug.h"
+#include "fdtable.h"
 
-
-void
-_gpgme_fd_table_init (fd_table_t fdt)
-{
-  fdt->fds = NULL;
-  fdt->size = 0;
-}
 
-void
-_gpgme_fd_table_deinit (fd_table_t fdt)
+/* Wrapper for the user wait handler to match the exported prototype.
+ * This is used by _gpgme_add_io_cb_user.  */
+static gpg_error_t
+user_io_cb_handler (void *data, int fd)
 {
-  if (fdt->fds)
-    free (fdt->fds);
-}
+  struct io_cb_tag_s *tag = data;
+  gpg_error_t err;
+  uint64_t serial;
+  gpgme_ctx_t ctx;
+  gpg_error_t op_err;
 
+  (void)fd;
 
-/* XXX We should keep a marker and roll over for speed.  */
-static gpgme_error_t
-fd_table_put (fd_table_t fdt, int fd, int dir, void *opaque, int *idx)
-{
-  unsigned int i, j;
-  struct io_select_fd_s *new_fds;
+  assert (data);
+  serial = tag->serial;
+  assert (serial);
 
-  for (i = 0; i < fdt->size; i++)
+  err = _gpgme_fdtable_run_io_cbs (serial, &op_err);
+  if (err || op_err)
+    ;
+  else if (!_gpgme_fdtable_io_cb_count (serial))
     {
-      if (fdt->fds[i].fd == -1)
-	break;
+      /* No more active callbacks - emit a DONE.  */
+      struct gpgme_io_event_done_data done_data =  { 0, 0 };
+      _gpgme_get_ctx (serial, &ctx);
+      if (ctx)
+        _gpgme_engine_io_event (ctx->engine, GPGME_EVENT_DONE, &done_data);
     }
-  if (i == fdt->size)
-    {
-#define FDT_ALLOCSIZE 10
-      new_fds = realloc (fdt->fds, (fdt->size + FDT_ALLOCSIZE)
-			 * sizeof (*new_fds));
-      if (!new_fds)
-	return gpg_error_from_syserror ();
-
-      fdt->fds = new_fds;
-      fdt->size += FDT_ALLOCSIZE;
-      for (j = 0; j < FDT_ALLOCSIZE; j++)
-	fdt->fds[i + j].fd = -1;
-    }
-
-  fdt->fds[i].fd = fd;
-  fdt->fds[i].for_read = (dir == 1);
-  fdt->fds[i].for_write = (dir == 0);
-  fdt->fds[i].signaled = 0;
-  fdt->fds[i].opaque = opaque;
-  *idx = i;
   return 0;
 }
 
+
 
 /* Register the file descriptor FD with the handler FNC (which gets
    FNC_DATA as its first argument) for the direction DIR.  DATA should
    be the context for which the fd is added.  R_TAG will hold the tag
-   that can be used to remove the fd.  */
+   that can be used to remove the fd.  This function is used for the
+   global and the private wait loops. */
 gpgme_error_t
 _gpgme_add_io_cb (void *data, int fd, int dir, gpgme_io_cb_t fnc,
 		  void *fnc_data, void **r_tag)
 {
   gpgme_error_t err;
   gpgme_ctx_t ctx = (gpgme_ctx_t) data;
-  fd_table_t fdt;
-  struct wait_item_s *item;
-  struct tag *tag;
+  struct io_cb_tag_s *tag;
+
+  TRACE_BEG  (DEBUG_SYSIO, __func__, NULL, "ctx=%lu fd=%d, dir %d",
+              CTXSERIAL (ctx), fd, dir);
+
+  if (!fnc)
+    return gpg_error (GPG_ERR_INV_ARG);
 
   assert (fnc);
   assert (ctx);
 
-  fdt = &ctx->fdt;
-  assert (fdt);
-
-  tag = malloc (sizeof *tag);
+  tag = calloc (1, sizeof *tag);
   if (!tag)
     return gpg_error_from_syserror ();
-  tag->ctx = ctx;
-
-  /* Allocate a structure to hold information about the handler.  */
-  item = calloc (1, sizeof *item);
-  if (!item)
-    {
-      free (tag);
-      return gpg_error_from_syserror ();
-    }
-  item->ctx = ctx;
-  item->dir = dir;
-  item->handler = fnc;
-  item->handler_value = fnc_data;
+  tag->serial = ctx->serial;
+  tag->fd = fd;
 
-  err = fd_table_put (fdt, fd, dir, item, &tag->idx);
+  err = _gpgme_fdtable_set_io_cb (fd, ctx->serial, dir, fnc, fnc_data);
   if (err)
     {
       free (tag);
-      free (item);
-      return err;
+      return TRACE_ERR (err);
     }
 
-  TRACE (DEBUG_CTX, "_gpgme_add_io_cb", NULL,
-         "ctx=%lu fd=%d dir=%d -> tag=%p", CTXSERIAL (ctx), fd, dir, tag);
-
   *r_tag = tag;
+
+  TRACE_SUC ("tag=%p", tag);
   return 0;
 }
 
 
+/* Register the file descriptor FD with the handler FNC (which gets
+   FNC_DATA as its first argument) for the direction DIR.  DATA should
+   be the context for which the fd is added.  R_TAG will hold the tag
+   that can be used to remove the fd.  This function is used for the
+   user wait loops. */
+gpg_error_t
+_gpgme_add_io_cb_user (void *data, int fd, int dir, gpgme_io_cb_t fnc,
+                       void *fnc_data, void **r_tag)
+{
+  gpgme_ctx_t ctx = (gpgme_ctx_t) data;
+  struct io_cb_tag_s *tag;
+  gpgme_error_t err;
+
+  TRACE_BEG  (DEBUG_SYSIO, __func__, NULL, "ctx=%lu fd=%d, dir %d",
+              CTXSERIAL (ctx), fd, dir);
+
+  assert (ctx);
+  err = _gpgme_add_io_cb (data, fd, dir, fnc, fnc_data, r_tag);
+  if (err)
+    return TRACE_ERR (err);
+  tag = *r_tag;
+  assert (tag);
+
+  err = ctx->user_io_cbs.add (ctx->user_io_cbs.add_priv, fd, dir,
+                              user_io_cb_handler, *r_tag,
+                              &tag->user_tag);
+  if (err)
+    _gpgme_remove_io_cb (*r_tag);
+  return TRACE_ERR (err);
+}
+
+
+/*  This function is used for the global and the private wait loops. */
 void
 _gpgme_remove_io_cb (void *data)
 {
-  struct tag *tag = data;
+  struct io_cb_tag_s *tag = data;
+  gpg_error_t err;
+
+  assert (tag);
+
+  err = _gpgme_fdtable_set_io_cb (tag->fd, tag->serial, 0, NULL, NULL);
+  if (err)
+    {
+      TRACE (DEBUG_CTX, __func__, NULL, "tag=%p (ctx=%lu fd=%d) failed: %s",
+             tag, tag->serial, tag->fd, gpg_strerror (err));
+    }
+  else
+    {
+      TRACE (DEBUG_CTX, __func__, NULL, "tag=%p (ctx=%lu fd=%d) done",
+             tag, tag->serial, tag->fd);
+    }
+  free (tag);
+}
+
+
+/* This function is used for the user wait loops. */
+void
+_gpgme_remove_io_cb_user (void *data)
+{
+  struct io_cb_tag_s *tag = data;
   gpgme_ctx_t ctx;
-  fd_table_t fdt;
-  int idx;
 
   assert (tag);
-  ctx = tag->ctx;
+  _gpgme_get_ctx (tag->serial, &ctx);
+
+  if (ctx)
+    ctx->user_io_cbs.remove (tag->user_tag);
+  _gpgme_remove_io_cb (data);
+}
+
+
+
+/* The internal I/O callback function used for the global event loop.
+   That loop is used for all asynchronous operations (except key
+   listing) for which no user I/O callbacks are specified.
+
+   A context sets up its initial I/O callbacks and then sends the
+   GPGME_EVENT_START event.  After that, it is added to the global
+   list of active contexts.
+
+   The gpgme_wait function contains a select() loop over all file
+   descriptors in all active contexts.  If an error occurs, it closes
+   all fds in that context and moves the context to the global done
+   list.  Likewise, if a context has removed all I/O callbacks, it is
+   moved to the global done list.
+
+   All contexts in the global done list are eligible for being
+   returned by gpgme_wait if requested by the caller.  */
+void
+_gpgme_wait_global_event_cb (void *data, gpgme_event_io_t type,
+			     void *type_data)
+{
+  gpgme_ctx_t ctx = (gpgme_ctx_t) data;
+  gpg_error_t err;
+
   assert (ctx);
-  fdt = &ctx->fdt;
-  assert (fdt);
-  idx = tag->idx;
 
-  TRACE (DEBUG_CTX, "_gpgme_remove_io_cb", NULL,
-         "ctx=%lu setting fd=%d (item=%p data=%p) done",
-         CTXSERIAL (ctx),
-         fdt->fds[idx].fd,
-         fdt->fds[idx].opaque, data);
+  switch (type)
+    {
+    case GPGME_EVENT_START:
+      {
+        err = _gpgme_fdtable_set_active (ctx->serial);
+	if (err)
+	  /* An error occurred.  Close all fds in this context, and
+	     send the error in a done event.  */
+	  _gpgme_cancel_with_err (ctx->serial, err, 0);
+      }
+      break;
 
-  free (fdt->fds[idx].opaque);
-  free (tag);
+    case GPGME_EVENT_DONE:
+      {
+	gpgme_io_event_done_data_t done_data =
+	  (gpgme_io_event_done_data_t) type_data;
+
+        _gpgme_fdtable_set_done (ctx->serial,
+                                 done_data->err, done_data->op_err);
+      }
+      break;
+
+    case GPGME_EVENT_NEXT_KEY:
+      assert (!"Unexpected event GPGME_EVENT_NEXT_KEY");
+      break;
+
+    case GPGME_EVENT_NEXT_TRUSTITEM:
+      assert (!"Unexpected event GPGME_EVENT_NEXT_TRUSTITEM");
+      break;
+
+    default:
+      assert (!"Unexpected event");
+      break;
+    }
+}
+
+
+/* The internal I/O callback function used for private event loops.
+ * The private event loops are used for all blocking operations, and
+ * for the key and trust item listing operations.  They are completely
+ * separated from each other.  */
+void
+_gpgme_wait_private_event_cb (void *data, gpgme_event_io_t type,
+			      void *type_data)
+{
+  switch (type)
+    {
+    case GPGME_EVENT_START:
+      /* Nothing to do here, as the wait routine is called after the
+	 initialization is finished.  */
+      break;
+
+    case GPGME_EVENT_DONE:
+      break;
+
+    case GPGME_EVENT_NEXT_KEY:
+      _gpgme_op_keylist_event_cb (data, type, type_data);
+      break;
+
+    case GPGME_EVENT_NEXT_TRUSTITEM:
+      _gpgme_op_trustlist_event_cb (data, type, type_data);
+      break;
+    }
+}
+
+
+/* The internal I/O callback function used for user event loops.  User
+ * event loops are used for all asynchronous operations for which a
+ * user callback is defined.  */
+void
+_gpgme_wait_user_event_cb (void *data, gpgme_event_io_t type, void *type_data)
+{
+  gpgme_ctx_t ctx = data;
 
-  /* Free the table entry.  */
-  fdt->fds[idx].fd = -1;
-  fdt->fds[idx].for_read = 0;
-  fdt->fds[idx].for_write = 0;
-  fdt->fds[idx].opaque = NULL;
+  if (ctx->user_io_cbs.event)
+    ctx->user_io_cbs.event (ctx->user_io_cbs.event_priv, type, type_data);
 }
 
+
 
-/* This is slightly embarrassing.  The problem is that running an I/O
-   callback _may_ influence the status of other file descriptors.  Our
-   own event loops could compensate for that, but the external event
-   loops cannot.  FIXME: We may still want to optimize this a bit when
-   we are called from our own event loops.  So if CHECKED is 1, the
-   check is skipped.  FIXME: Give an example on how the status of other
-   fds can be influenced.  */
+/* Perform asynchronous operations in the global event loop (ie, any
+   asynchronous operation except key listing and trustitem listing
+   operations).  If CTX is not a null pointer, the function will
+   return if the asynchronous operation in the context CTX finished.
+   Otherwise the function will return if any asynchronous operation
+   finished.  If HANG is zero, the function will not block for a long
+   time.  Otherwise the function does not return until an operation
+   matching CTX finished.
+
+   If a matching context finished, it is returned, and *STATUS is set
+   to the error value of the operation in that context.  Otherwise, if
+   the timeout expires, NULL is returned and *STATUS is 0.  If an
+   error occurs, NULL is returned and *STATUS is set to the error
+   value.  */
+gpgme_ctx_t
+gpgme_wait_ext (gpgme_ctx_t ctx, gpgme_error_t *status,
+		gpgme_error_t *op_err, int hang)
+{
+  gpg_error_t err;
+  io_select_t fds = NULL;
+  unsigned int nfds;
+  int nr;
+  uint64_t serial;
+
+  do
+    {
+      /* Get all fds of CTX (or all if CTX is NULL) we want to wait
+       * for and which are in the active state.  */
+      free (fds);
+      nfds = _gpgme_fdtable_get_fds (&fds, ctx? ctx->serial : 0,
+                                     ( FDTABLE_FLAG_ACTIVE
+                                       | FDTABLE_FLAG_CLEAR));
+      if (!nfds)
+        {
+          err = gpg_error_from_syserror ();
+          if (gpg_err_code (err) != GPG_ERR_MISSING_ERRNO)
+            {
+              if (status)
+                *status = err;
+              if (op_err)
+                *op_err = 0;
+              free (fds);
+              return NULL;
+            }
+          /* Nothing to select.  Run the select anyway, so that we use
+           * its timeout.  */
+        }
+
+      nr = _gpgme_io_select (fds, nfds, 0);
+      if (nr < 0)
+        {
+          if (status)
+            *status = gpg_error_from_syserror ();
+          if (op_err)
+            *op_err = 0;
+          free (fds);
+          return NULL;
+        }
+      _gpgme_fdtable_set_signaled (fds, nfds);
+
+      _gpgme_fdtable_run_io_cbs (ctx? ctx->serial : 0, NULL);
+      serial = _gpgme_fdtable_get_done (ctx? ctx->serial : 0, status, op_err);
+      if (serial)
+        {
+          _gpgme_get_ctx (serial, &ctx);
+          hang = 0;
+        }
+      else if (!hang)
+        {
+          ctx = NULL;
+          if (status)
+            *status = 0;
+          if (op_err)
+            *op_err = 0;
+        }
+    }
+  while (hang);
+
+  free (fds);
+  return ctx;
+}
+
+
+gpgme_ctx_t
+gpgme_wait (gpgme_ctx_t ctx, gpgme_error_t *status, int hang)
+{
+  return gpgme_wait_ext (ctx, status, NULL, hang);
+}
+
+
+
+/* If COND is a null pointer, wait until the blocking operation in CTX
+   finished and return its error value.  Otherwise, wait until COND is
+   satisfied or the operation finished.  */
 gpgme_error_t
-_gpgme_run_io_cb (struct io_select_fd_s *an_fds, int checked,
-		  gpgme_error_t *op_err)
+_gpgme_wait_on_condition (gpgme_ctx_t ctx, volatile int *cond,
+			  gpgme_error_t *r_op_err)
 {
-  struct wait_item_s *item;
-  struct io_cb_data iocb_data;
-  gpgme_error_t err;
+  gpgme_error_t err = 0;
+  int hang = 1;
+  io_select_t fds = NULL;
+  unsigned int nfds;
+  int op_err;
+  int nr;
+
+  if (r_op_err)
+    *r_op_err = 0;
 
-  item = (struct wait_item_s *) an_fds->opaque;
-  assert (item);
+  if (!ctx)
+    return gpg_error (GPG_ERR_INV_VALUE);
 
-  if (!checked)
+  do
     {
-      int nr;
-      struct io_select_fd_s fds;
-
-      TRACE (DEBUG_CTX, "_gpgme_run_io_cb", item, "need to check");
-      fds = *an_fds;
-      fds.signaled = 0;
-      /* Just give it a quick poll.  */
-      nr = _gpgme_io_select (&fds, 1, 1);
-      assert (nr <= 1);
+      /* Get all fds of CTX we want to wait for.  */
+      free (fds);
+      nfds = _gpgme_fdtable_get_fds (&fds, ctx->serial,
+                                     FDTABLE_FLAG_CLEAR);
+      if (!nfds)
+        {
+          err = gpg_error_from_syserror ();
+          if (gpg_err_code (err) != GPG_ERR_MISSING_ERRNO)
+            {
+              free (fds);
+              return err;
+            }
+          /* Nothing to select.  Run the select anyway, so that we use
+           * its timeout.  */
+        }
+
+      nr = _gpgme_io_select (fds, nfds, 0);
       if (nr < 0)
-	return gpg_error_from_syserror ();
-      else if (nr == 0)
+	{
+	  /* An error occurred.  Close all fds in this context, and
+	     signal it.  */
+	  err = gpg_error_from_syserror ();
+          _gpgme_cancel_with_err (ctx->serial, err, 0);
+          free (fds);
+	  return err;
+	}
+      _gpgme_fdtable_set_signaled (fds, nfds);
+
+      err = _gpgme_fdtable_run_io_cbs (ctx->serial, r_op_err);
+      if (err || (r_op_err && *r_op_err))
         {
-          /* The status changed in the meantime, there is nothing left
-           * to do.  */
-          return 0;
+          free (fds);
+          return err;
         }
+
+      if (!_gpgme_fdtable_io_cb_count (ctx->serial))
+	{
+	  struct gpgme_io_event_done_data data = {0, 0};
+	  _gpgme_engine_io_event (ctx->engine, GPGME_EVENT_DONE, &data);
+	  hang = 0;
+	}
+      if (cond && *cond)
+	hang = 0;
     }
+  while (hang);
 
-  TRACE (DEBUG_CTX, "_gpgme_run_io_cb", item, "handler (%p, %d)",
-          item->handler_value, an_fds->fd);
+  free (fds);
+  return 0;
+}
 
-  iocb_data.handler_value = item->handler_value;
-  iocb_data.op_err = 0;
-  err = item->handler (&iocb_data, an_fds->fd);
 
-  *op_err = iocb_data.op_err;
-  return err;
+/* Wait until the blocking operation in context CTX has finished and
+   return the error value.  This variant can not be used for
+   session-based protocols.  */
+gpgme_error_t
+_gpgme_wait_one (gpgme_ctx_t ctx)
+{
+  return _gpgme_wait_on_condition (ctx, NULL, NULL);
+}
+
+/* Wait until the blocking operation in context CTX has finished and
+   return the error value.  This is the right variant to use for
+   sesion-based protocols.  */
+gpgme_error_t
+_gpgme_wait_one_ext (gpgme_ctx_t ctx, gpgme_error_t *op_err)
+{
+  return _gpgme_wait_on_condition (ctx, NULL, op_err);
 }
diff --git a/src/wait.h b/src/wait.h
index 4beac6e1..b7584cf5 100644
--- a/src/wait.h
+++ b/src/wait.h
@@ -1,6 +1,6 @@
 /* wait.h - Definitions for the wait queue interface.
    Copyright (C) 2000 Werner Koch (dd9jn)
-   Copyright (C) 2001, 2002, 2003, 2004 g10 Code GmbH
+   Copyright (C) 2001, 2002, 2003, 2004. 2019 g10 Code GmbH
 
    This file is part of GPGME.
 
@@ -25,58 +25,46 @@
 #include "gpgme.h"
 #include "sema.h"
 
-struct fd_table
+/* A registered fd handler can be removed using the tag that
+ * identifies it.  In the public API that tag is an an opaque
+ * pointer. */
+struct io_cb_tag_s
 {
-  struct io_select_fd_s *fds;
-  size_t size;
-};
-typedef struct fd_table *fd_table_t;
+  /* The s/n of the context for which the fd was registered.  */
+  uint64_t serial;
 
-/* Wait items are hooked into the io_select_fd_s to connect an fd with
-   a callback handler.  */
-struct wait_item_s
-{
-  gpgme_ctx_t ctx;
-  gpgme_io_cb_t handler;
-  void *handler_value;
-  int dir;
-};
-
-/* A registered fd handler is removed later using the tag that
-   identifies it.  */
-struct tag
-{
-  /* The context for which the fd was registered.  */
-  gpgme_ctx_t ctx;
-
-  /* The index into the fd table for this context.  */
-  int idx;
+  /* The actual fd.  */
+  int fd;
 
   /* This is used by the wrappers for the user event loop.  */
   void *user_tag;
-};
 
+  /* A string used describing the data.  This is used for tracing.  */
+  const char *desc;
+};
 
-void _gpgme_fd_table_init (fd_table_t fdt);
-void _gpgme_fd_table_deinit (fd_table_t fdt);
 
 gpgme_error_t _gpgme_add_io_cb (void *data, int fd, int dir,
-			     gpgme_io_cb_t fnc, void *fnc_data, void **r_tag);
+                                gpgme_io_cb_t fnc, void *fnc_data,
+                                void **r_tag);
+gpgme_error_t _gpgme_add_io_cb_user (void *data, int fd, int dir,
+                                     gpgme_io_cb_t fnc, void *fnc_data,
+                                     void **r_tag);
+
 void _gpgme_remove_io_cb (void *tag);
-void _gpgme_wait_private_event_cb (void *data, gpgme_event_io_t type,
-				   void *type_data);
+void _gpgme_remove_io_cb_user (void *tag);
+
+
 void _gpgme_wait_global_event_cb (void *data, gpgme_event_io_t type,
 				  void *type_data);
 
-gpgme_error_t _gpgme_wait_user_add_io_cb (void *data, int fd, int dir,
-					  gpgme_io_cb_t fnc, void *fnc_data,
-					  void **r_tag);
-void _gpgme_wait_user_remove_io_cb (void *tag);
+
+void _gpgme_wait_private_event_cb (void *data, gpgme_event_io_t type,
+				   void *type_data);
 void _gpgme_wait_user_event_cb (void *data, gpgme_event_io_t type,
 				void *type_data);
 
-gpgme_error_t _gpgme_run_io_cb (struct io_select_fd_s *an_fds, int checked,
-				gpgme_error_t *err);
+
 
 
 /* Session based interfaces require to make a distinction between IPC