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Commit 43fa87f7 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf/core: Fix another perf,trace,cpuhp lock inversion 



Lockdep noticed the following 3-way lockup race:

        perf_trace_init()
 #0       mutex_lock(&event_mutex)
          perf_trace_event_init()
            perf_trace_event_reg()
              tp_event->class->reg() := tracepoint_probe_register
 #1              mutex_lock(&tracepoints_mutex)
                  trace_point_add_func()
 #2                  static_key_enable()

 #2	do_cpu_up()
	  perf_event_init_cpu()
 #3	    mutex_lock(&pmus_lock)
 #4	    mutex_lock(&ctx->mutex)

	perf_ioctl()
 #4	  ctx = perf_event_ctx_lock()
	  _perf_iotcl()
	    ftrace_profile_set_filter()
 #0	      mutex_lock(&event_mutex)

Fudge it for now by noting that the tracepoint state does not depend
on the event <-> context relation. Ugly though :/

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 82d94856

kernel/events/core.c

+24 −2
Original line number Diff line number Diff line
@@ -8525,6 +8525,29 @@ perf_event_set_addr_filter(struct perf_event *event, char *filter_str) 
	return ret;

}



static int

perf_tracepoint_set_filter(struct perf_event *event, char *filter_str)

{

	struct perf_event_context *ctx = event->ctx;

	int ret;



	/*

	 * Beware, here be dragons!!

	 *

	 * the tracepoint muck will deadlock against ctx->mutex, but the tracepoint

	 * stuff does not actually need it. So temporarily drop ctx->mutex. As per

	 * perf_event_ctx_lock() we already have a reference on ctx.

	 *

	 * This can result in event getting moved to a different ctx, but that

	 * does not affect the tracepoint state.

	 */

	mutex_unlock(&ctx->mutex);

	ret = ftrace_profile_set_filter(event, event->attr.config, filter_str);

	mutex_lock(&ctx->mutex);



	return ret;

}



static int perf_event_set_filter(struct perf_event *event, void __user *arg)

{

	char *filter_str;
@@ -8541,8 +8564,7 @@ static int perf_event_set_filter(struct perf_event *event, void __user *arg) 


	if (IS_ENABLED(CONFIG_EVENT_TRACING) &&

	    event->attr.type == PERF_TYPE_TRACEPOINT)

		ret = ftrace_profile_set_filter(event, event->attr.config,

						filter_str);

		ret = perf_tracepoint_set_filter(event, filter_str);

	else if (has_addr_filter(event))

		ret = perf_event_set_addr_filter(event, filter_str);