Messages in this thread | | | Date | Wed, 19 Oct 2011 09:00:37 -0700 | From | Greg KH <> | Subject | Re: Patch Upstream: cputimer: Cure lock inversion |
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On Wed, Oct 19, 2011 at 11:55:01AM -0400, Josh Boyer wrote: > On Wed, Oct 19, 2011 at 11:49 AM, Greg KH <greg@kroah.com> wrote: > > On Wed, Oct 19, 2011 at 11:39:14AM -0400, Gregs git-bot wrote: > >> commit: bcd5cff7216f9b2de0a148cc355eac199dc6f1cf > >> From: Peter Zijlstra <a.p.zijlstra@chello.nl> > >> Date: Mon, 17 Oct 2011 11:50:30 +0200 > >> Subject: cputimer: Cure lock inversion > >> > >> 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"). > > > > There is no such patch in Linus's tree that I can find. So, what > > problem is this really trying to cure here and what kernel did it show > > up in? > > Uh... > > bcd5cff7216f9b2de0a148cc355eac199dc6f1cf is the upstream commit (post -rc10).
No, I understand that this is the commit I just referenced.
I'm talking about the "This problem was introduced..." line in the commit. I want to find out what was the original problem that this patch is fixing, to determine how far back in the -stable series I need to backport this to.
The issue is that there is no e8abccb7193 ("posix-cpu-timers: Cure SMP accounting oddities") commit that I can see in Linus's tree right now.
> This thread covers the conversation (it's long): > > http://thread.gmane.org/gmane.linux.kernel/1199406/focus=1204676
Ugh, I'll go dig, but help would be appreciated...
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