Messages in this thread Patch in this message | | | Subject | [PATCH] sched/clock: prevent tracing recursion in sched_clock_cpu() | From | Fernando Luis Vázquez Cao <> | Date | Thu, 06 Mar 2014 14:25:28 +0900 |
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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").
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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