Hi Borislav, On Tue, 26 Mar 2013 19:34:52 +0100, Borislav Petkov wrote: > On Sun, Mar 24, 2013 at 04:59:24PM +0100, Borislav Petkov wrote: >> On Sun, Mar 24, 2013 at 12:55:56PM +0100, Borislav Petkov wrote: >> > Hi, >> > >> > so I was tracing a small .c program like so: >> > >> > $ ./perf record ~/test/asm >> > >> > and here's what got spewed in dmesg. Kernel is plain -rc4. Any pending >> > fixes in tip I should try? >> > >> > [ 3700.194208] BUG: using smp_processor_id() in preemptible [00000000] >> > code: asm/8333 >> > [ 3700.194226] caller is perf_event_task_ctx+0x55/0x140 >> >> Ok, here's the call stack I was able to reconstruct: >> >> perf_event_exit_task() >> |->perf_event_exit_task_context() >> |-> perf_event_task() >> |-> perf_event_task_event() >> |-> perf_event_task_ctx() >> |-> perf_event_task_match() >> |-> event_filter_match() >> |-> smp_processor_id() -> debug_smp_processor_id() > > Ok, jolsa just rootcaused it: It is caused by > d610d98b5de6860feb21539726e9af7c9094151c calling perf_event_task_ctx() > outside of the preempt-safe protection.
Oops, my bad. Forgot to enable CONFIG_DEBUG_PREEMPT when testing. :( > > There's a straightforward fix below, what to people think? Looks okay to me. Thanks for fixing this! Namhyung > > -- > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 7b4a55d41efc..f3bb3384a106 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -4455,8 +4455,11 @@ static void perf_event_task_event(struct > perf_task_event *task_event) > next: > put_cpu_ptr(pmu->pmu_cpu_context); > } > + > + preempt_disable(); > if (task_event->task_ctx) > perf_event_task_ctx(task_event->task_ctx, task_event); > + preempt_enable(); > > rcu_read_unlock(); > } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
