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| author | Vasiliy Kulikov <segoon@openwall.com> | 2011-08-03 22:28:26 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-08-03 14:45:55 -1000 |
| commit | 298507d4d2cff2248e84afcf646b697301294442 (patch) | |
| tree | 15861e6610403c57cf4eca976dea4d59ac7a8e99 /ipc/shm.c | |
| parent | 33a30ed4bdccd95ed84a1a20c1fef8ac89788ce5 (diff) | |
| download | lwn-298507d4d2cff2248e84afcf646b697301294442.tar.gz lwn-298507d4d2cff2248e84afcf646b697301294442.zip | |
shm: optimize exit_shm()
We may optimistically check .in_use == 0 without holding the rw_mutex:
it's the common case, and if it's zero, there certainly won't be any
segments associated with us.
After taking the lock, the idr_for_each() will do the right thing, so we
could now drop the re-check inside the lock without any real cost. But
it won't hurt.
Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/shm.c')
| -rw-r--r-- | ipc/shm.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index 7efff043ffbf..b5bae9d945b6 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -304,6 +304,9 @@ void exit_shm(struct task_struct *task) { struct ipc_namespace *ns = task->nsproxy->ipc_ns; + if (shm_ids(ns).in_use == 0) + return; + /* Destroy all already created segments, but not mapped yet */ down_write(&shm_ids(ns).rw_mutex); if (shm_ids(ns).in_use) |