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Do a lockless read of the audit pipe list before grabbing the audit pipe

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lock in order to avoid the lock acquire hit if the pipe list is very
likely empty.

Obtained from:	TrustedBSD Project
MFC after:	3 weeks
Sponsored by:	Apple, Inc.
This commit is contained in:
Robert Watson 2009-01-06 14:15:38 +00:00
parent 16c6e0979c
commit d423f266c4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=186825
1 changed files with 4 additions and 0 deletions
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4
sys/security/audit/audit_pipe.c
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@ -436,6 +436,10 @@ audit_pipe_preselect(au_id_t auid, au_event_t event, au_class_t class,
{
struct audit_pipe *ap;
/* Lockless read to avoid acquiring the global lock if not needed. */
if (TAILQ_EMPTY(&audit_pipe_list))
return (0);
AUDIT_PIPE_LIST_RLOCK();
TAILQ_FOREACH(ap, &audit_pipe_list, ap_list) {
AUDIT_PIPE_LOCK(ap);