| From tglx@linutronix.de Wed Feb 21 16:28:30 2007 |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Thu, 22 Feb 2007 01:33:29 +0100 |
| Subject: Fix posix-cpu-timer breakage caused by stale p->last_ran value |
| To: Andrew Morton <akpm@linux-foundation.org> |
| Cc: Ingo Molnar <mingo@elte.hu>, john stultz <johnstul@us.ibm.com>, Roman Zippel <zippel@linux-m68k.org>, Mike Galbraith <efault@gmx.de>, Ken Chen <kenneth.w.chen@intel.com>, balducci@units.it, Greg KH <greg@kroah.com> |
| Message-ID: <1172104409.25076.165.camel@localhost.localdomain> |
| |
| From: Thomas Gleixner <tglx@linutronix.de> |
| |
| Problem description at: |
| http://bugzilla.kernel.org/show_bug.cgi?id=8048 |
| |
| Commit b18ec80396834497933d77b81ec0918519f4e2a7 |
| [PATCH] sched: improve migration accuracy |
| optimized the scheduler time calculations, but broke posix-cpu-timers. |
| |
| The problem is that the p->last_ran value is not updated after a context |
| switch. So a subsequent call to current_sched_time() calculates with a |
| stale p->last_ran value, i.e. accounts the full time, which the task was |
| scheduled away. |
| |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Acked-by: Ingo Molnar <mingo@elte.hu> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| kernel/sched.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- linux-2.6.20.1.orig/kernel/sched.c |
| +++ linux-2.6.20.1/kernel/sched.c |
| @@ -3547,7 +3547,7 @@ switch_tasks: |
| |
| sched_info_switch(prev, next); |
| if (likely(prev != next)) { |
| - next->timestamp = now; |
| + next->timestamp = next->last_ran = now; |
| rq->nr_switches++; |
| rq->curr = next; |
| ++*switch_count; |
