sched: Fix lockup by limiting load-balance retries on lock-break

Eric and David reported dead machines and traced it to commit
a195f004 ("sched: Fix load-balance lock-breaking"), it turns out
there's still a scenario where we can end up re-trying forever.

Since there is no strict forward progress guarantee in the
load-balance iteration we can get stuck re-retrying the same
task-set over and over.

Creating a forward progress guarantee with the existing
structure is somewhat non-trivial, for now simply terminate the
retry loop after a few tries.

Reported-by: Eric Dumazet <[email protected]>
Tested-by: Eric Dumazet <[email protected]>
Reported-by: David Ahern <[email protected]>
[ logic cleanup as suggested by Eric ]
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Suresh Siddha <[email protected]>
Link: http://lkml.kernel.org/r/1326297936.2442.157.camel@twins
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions