Messages in this thread | | | Date | Thu, 6 Mar 2014 05:51:13 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] sched/clock: prevent tracing recursion in sched_clock_cpu() |
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On Thu, 06 Mar 2014 14:25:28 +0900 Fernando Luis Vázquez Cao <fernando_b1@lab.ntt.co.jp> wrote:
> From: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> > > Prevent tracing of preempt_disable/enable() in sched_clock_cpu(). > When CONFIG_DEBUG_PREEMPT is enabled, preempt_disable/enable() are > traced and this causes trace_clock() users (and probably others) to > go into an infinite recursion. Systems with a stable sched_clock() > are not affected. > > This problem is similar to that fixed by upstream commit 95ef1e52922 > ("KVM guest: prevent tracing recursion with kvmclock").
Also similar to: 569d6557ab957.
Acked-by: Steven Rostedt <rostedt@goodmis.org>
-- Steve
> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Steven Rostedt <rostedt@goodmis.org> > Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp> > --- > > diff -urNp linux-3.14-rc5-orig/kernel/sched/clock.c linux-3.14-rc5/kernel/sched/clock.c > --- linux-3.14-rc5-orig/kernel/sched/clock.c 2014-03-06 13:37:43.567720550 +0900 > +++ linux-3.14-rc5/kernel/sched/clock.c 2014-03-06 13:41:56.937100949 +0900 > @@ -301,14 +301,14 @@ u64 sched_clock_cpu(int cpu) > if (unlikely(!sched_clock_running)) > return 0ull; > > - preempt_disable(); > + preempt_disable_notrace(); > scd = cpu_sdc(cpu); > > if (cpu != smp_processor_id()) > clock = sched_clock_remote(scd); > else > clock = sched_clock_local(scd); > - preempt_enable(); > + preempt_enable_notrace(); > > return clock; > } >
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