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| author | Manfred Spraul <manfred@colorfullife.com> | 2013-09-30 13:45:06 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-10-18 07:45:48 -0700 |
| commit | 901f6fedc5340d66e2ca67c70dfee926cb5a1ea0 (patch) | |
| tree | 95fbc8a2a729c57538e3aba54c84fe380a20c50f /ipc/compat.c | |
| parent | 184076a9f9306c9bef6843bf4cc7b7e15b8fc7b4 (diff) | |
| download | lwn-901f6fedc5340d66e2ca67c70dfee926cb5a1ea0.tar.gz lwn-901f6fedc5340d66e2ca67c70dfee926cb5a1ea0.zip | |
ipc/sem.c: optimize sem_lock()
commit 6d07b68ce16ae9535955ba2059dedba5309c3ca1 upstream.
Operations that need access to the whole array must guarantee that there
are no simple operations ongoing. Right now this is achieved by
spin_unlock_wait(sem->lock) on all semaphores.
If complex_count is nonzero, then this spin_unlock_wait() is not
necessary, because it was already performed in the past by the thread
that increased complex_count and even though sem_perm.lock was dropped
inbetween, no simple operation could have started, because simple
operations cannot start when complex_count is non-zero.
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'ipc/compat.c')
0 files changed, 0 insertions, 0 deletions