lib/atomic64_test.c: add a test that atomic64_inc_not_zero() returns an int

atomic64_inc_not_zero() returns a "truth value" which in C is
traditionally an int.  That means callers are likely to expect the
result will fit in an int.

If an implementation returns a "true" value which does not fit in an
int, then there's a possibility that callers will truncate it when they
store it in an int.

In fact this happened in practice, see commit 966d2b04e070
("percpu-refcount: fix reference leak during percpu-atomic transition").

So add a test that the result fits in an int, even when the input
doesn't.  This catches the case where an implementation just passes the
non-zero input value out as the result.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michael Ellerman <[email protected]>
Cc: Douglas Miller <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions