svn commit: r300110 - head/sys/kern

Mark Johnston markj at FreeBSD.org
Wed May 18 03:55:55 UTC 2016


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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