On 2021/10/12 下午7:20, Peter Zijlstra wrote: > On Tue, Oct 12, 2021 at 01:40:31PM +0800, 王贇 wrote: > >> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c >> index 6aed10e..33c2f76 100644 >> --- a/kernel/trace/trace_event_perf.c >> +++ b/kernel/trace/trace_event_perf.c >> @@ -441,12 +441,19 @@ void perf_trace_buf_update(void *record, u16 type) >> if (!rcu_is_watching()) >> return; >> >> + /* >> + * Prevent CPU changing from now on. rcu must >> + * be in watching if the task was migrated and >> + * scheduled. >> + */ >> + preempt_disable_notrace(); >> + >> if ((unsigned long)ops->private != smp_processor_id()) >> - return; >> + goto out; >> >> bit = ftrace_test_recursion_trylock(ip, parent_ip); >> if (bit < 0) >> - return; >> + goto out; >> >> event = container_of(ops, struct perf_event, ftrace_ops); >> > > This seems rather daft, wouldn't it be easier to just put that check > under the recursion thing? In case if the condition matched, extra lock/unlock will be introduced, but I guess that's acceptable since this seems unlikely to happen :-P Will move the check in v2. Regards, Michael Wang >
