src/patches/suse-2.6.27.39/patches.fixes/bug-437171_1_sched_clock_lock.patch

   1 Subject: sched: only update rq->clock while holding rq->lock
   2 From: Peter Zijlstra <a.p.zijlstra@chello.nl>
   3 References: 437171 - LTC47404
   4
   5 Vatsa noticed rq->clock going funny and tracked it down to an update_rq_clock()
   6 outside a rq->lock section.
   7
   8 This is a problem because things like double_rq_lock() update the rq->clock
   9 value for both rqs. Therefore disabling interrupts isn't strong enough.
  10
  11 Reported-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
  12 Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
  13 Signed-off-by: Ingo Molnar <mingo@elte.hu>
  14 Signed-off-by: Olaf Hering <olh@suse.de>
  15
  16 ---
  17  kernel/sched.c |    5 +----
  18  1 file changed, 1 insertion(+), 4 deletions(-)
  19
  20 --- a/kernel/sched.c
  21 +++ b/kernel/sched.c
  22 @@ -4449,12 +4449,9 @@ need_resched_nonpreemptible:
  23         if (sched_feat(HRTICK))
  24                 hrtick_clear(rq);
  25
  26 -       /*
  27 -        * Do the rq-clock update outside the rq lock:
  28 -        */
  29         local_irq_disable();
  30 -       update_rq_clock(rq);
  31         spin_lock(&rq->lock);
  32 +       update_rq_clock(rq);
  33         clear_tsk_need_resched(prev);
  34
  35         if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {