δΊ 2015/10/13 3:20, Alexei Starovoitov ει: > On 10/12/15 2:02 AM, Kaixu Xia wrote: >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index f57d7fe..25e073d 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -39,6 +39,7 @@ struct bpf_map { >> u32 max_entries; >> const struct bpf_map_ops *ops; >> struct work_struct work; >> + atomic_t perf_sample_disable; >> }; >> >> struct bpf_map_type_list { >> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h >> index 092a0e8..0606d1d 100644 >> --- a/include/linux/perf_event.h >> +++ b/include/linux/perf_event.h >> @@ -483,6 +483,8 @@ struct perf_event { >> perf_overflow_handler_t overflow_handler; >> void *overflow_handler_context; >> >> + atomic_t *sample_disable; > > this looks fragile and unnecessary. > Why add such field to generic bpf_map and carry its pointer into perf_event? > Single extra field in perf_event would have been enough. > Even better is to avoid adding any fields. > There is already event->state why not to use that? > The proper perf_event_enable/disable are so heavy that another > mechanism needed? cpu_function_call is probably too much to do > from bpf program, but that can be simplified? > Based on the use case from cover letter, sounds like you want > something like soft_disable? > Then extending event->state would make the most sense. > Also consider the case of re-entrant event enable/disable. > So inc/dec of a flag may be needed?
Thanks for your comments! I've tried perf_event_enable/disable, but there is a warning caused by cpu_function_call. The main reason as follows, int smp_call_function_single(...) { ... WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() && !oops_in_progress); ... } So I added the extra atomic flag filed in order to avoid this problem. > > > . > -- 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/