summaryrefslogtreecommitdiffstats
path: root/security/keys
diff options
context:
space:
mode:
authorNick Piggin <npiggin@suse.de>2009-12-15 16:47:30 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-16 07:20:09 -0800
commitd4212093dca95c1f52197017d969cc66d5d962aa (patch)
treef52484ae3c7b3034715b5745ae2b7db3906ab022 /security/keys
parent9cad200c7686708b326520a45dd680a4147568a6 (diff)
ipc/sem.c: sem preempt improve
The strange sysv semaphore wakeup scheme has a kind of busy-wait lock involved, which could deadlock if preemption is enabled during the "lock". It is an implementation detail (due to a spinlock being held) that this is actually the case. However if "spinlocks" are made preemptible, or if the sem lock is changed to a sleeping lock for example, then the wakeup would become buggy. So this might be a bugfix for -rt kernels. Imagine waker being preempted by wakee and never clearing IN_WAKEUP -- if wakee has higher RT priority then there is a priority inversion deadlock. Even if there is not a priority inversion to cause a deadlock, then there is still time wasted spinning. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Pierre Peiffer <peifferp@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'security/keys')
0 files changed, 0 insertions, 0 deletions