diff options
Diffstat (limited to 'cputimer-cure-lock-inversion.patch')
-rw-r--r-- | cputimer-cure-lock-inversion.patch | 73 |
1 files changed, 0 insertions, 73 deletions
diff --git a/cputimer-cure-lock-inversion.patch b/cputimer-cure-lock-inversion.patch deleted file mode 100644 index cebb775bf..000000000 --- a/cputimer-cure-lock-inversion.patch +++ /dev/null @@ -1,73 +0,0 @@ -Subject: cputimer: Cure lock inversion -From: Peter Zijlstra <a.p.zijlstra@chello.nl> -Date: Mon Oct 17 11:50:30 CEST 2011 - -There's a lock inversion between the cputimer->lock and rq->lock; notably -the two callchains involved are: - - update_rlimit_cpu() - sighand->siglock - set_process_cpu_timer() - cpu_timer_sample_group() - thread_group_cputimer() - cputimer->lock - thread_group_cputime() - task_sched_runtime() - ->pi_lock - rq->lock - - scheduler_tick() - rq->lock - task_tick_fair() - update_curr() - account_group_exec() - cputimer->lock - -Where the first one is enabling a CLOCK_PROCESS_CPUTIME_ID timer, and -the second one is keeping up-to-date. - -This problem was introduced by e8abccb7193 ("posix-cpu-timers: Cure -SMP accounting oddities"). - -Cure the problem by removing the cputimer->lock and rq->lock nesting, -this leaves concurrent enablers doing duplicate work, but the time -wasted should be on the same order otherwise wasted spinning on the -lock and the greater-than assignment filter should ensure we preserve -monotonicity. - -Reported-by: Dave Jones <davej@redhat.com> -Reported-by: Simon Kirby <sim@hostway.ca> -Cc: stable@kernel.org -Cc: Thomas Gleixner <tglx@linutronix.de> -Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> ---- - kernel/posix-cpu-timers.c | 7 ++++--- - 1 file changed, 4 insertions(+), 3 deletions(-) -Index: linux-2.6/kernel/posix-cpu-timers.c -=================================================================== ---- linux-2.6.orig/kernel/posix-cpu-timers.c -+++ linux-2.6/kernel/posix-cpu-timers.c -@@ -274,9 +274,7 @@ void thread_group_cputimer(struct task_s - struct task_cputime sum; - unsigned long flags; - -- spin_lock_irqsave(&cputimer->lock, flags); - if (!cputimer->running) { -- cputimer->running = 1; - /* - * The POSIX timer interface allows for absolute time expiry - * values through the TIMER_ABSTIME flag, therefore we have -@@ -284,8 +282,11 @@ void thread_group_cputimer(struct task_s - * it. - */ - thread_group_cputime(tsk, &sum); -+ spin_lock_irqsave(&cputimer->lock, flags); -+ cputimer->running = 1; - update_gt_cputime(&cputimer->cputime, &sum); -- } -+ } else -+ spin_lock_irqsave(&cputimer->lock, flags); - *times = cputimer->cputime; - spin_unlock_irqrestore(&cputimer->lock, flags); - } - |