Author: markj
Date: Wed May 18 03:55:54 2016
New Revision: 300110
URL: https://svnweb.freebsd.org/changeset/base/300110
Log:
Do not acquire the thread lock in hardclock_cnt() unless needed.
This function only sets thread flags if a SIGPROF or SIGVTALRM timer
has fired, which is almost never the case.
MFC after: 2 weeks
Modified:
head/sys/kern/kern_clock.c
Modified: head/sys/kern/kern_clock.c
==============================================================================
--- head/sys/kern/kern_clock.c Wed May 18 03:50:21 2016 (r300109)
+++ head/sys/kern/kern_clock.c Wed May 18 03:55:54 2016 (r300110)
@@ -570,9 +570,11 @@ hardclock_cnt(int cnt, int usermode)
flags |= TDF_PROFPEND | TDF_ASTPENDING;
PROC_ITIMUNLOCK(p);
}
- thread_lock(td);
- td->td_flags |= flags;
- thread_unlock(td);
+ if (flags != 0) {
+ thread_lock(td);
+ td->td_flags |= flags;
+ thread_unlock(td);
+ }
#ifdef HWPMC_HOOKS
if (PMC_CPU_HAS_SAMPLES(PCPU_GET(cpuid)))
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