Commit c6df8d5a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf: Fix crash in swevents 



Frederic reported that because swevents handling doesn't disable IRQs
anymore, we can get a recursion of perf_adjust_period(), once from
overflow handling and once from the tick.

If both call ->disable, we get a double hlist_del_rcu() and trigger
a LIST_POISON2 dereference.

Since we don't actually need to stop/start a swevent to re-programm
the hardware (lack of hardware to program), simply nop out these
callbacks for the swevent pmu.

Reported-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1275557609.27810.35218.camel@twins>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent da3fd1a0

kernel/perf_event.c

+15 −9
Original line number Diff line number Diff line
@@ -4055,13 +4055,6 @@ static void perf_swevent_overflow(struct perf_event *event, u64 overflow, 
	}

}



static void perf_swevent_unthrottle(struct perf_event *event)

{

	/*

	 * Nothing to do, we already reset hwc->interrupts.

	 */

}



static void perf_swevent_add(struct perf_event *event, u64 nr,

			       int nmi, struct perf_sample_data *data,

			       struct pt_regs *regs)
@@ -4276,11 +4269,22 @@ static void perf_swevent_disable(struct perf_event *event) 
	hlist_del_rcu(&event->hlist_entry);

}



static void perf_swevent_void(struct perf_event *event)

{

}



static int perf_swevent_int(struct perf_event *event)

{

	return 0;

}



static const struct pmu perf_ops_generic = {

	.enable		= perf_swevent_enable,

	.disable	= perf_swevent_disable,

	.start		= perf_swevent_int,

	.stop		= perf_swevent_void,

	.read		= perf_swevent_read,

	.unthrottle	= perf_swevent_unthrottle,

	.unthrottle	= perf_swevent_void, /* hwc->interrupts already reset */

};



/*
@@ -4561,8 +4565,10 @@ static int swevent_hlist_get(struct perf_event *event) 
static const struct pmu perf_ops_tracepoint = {

	.enable		= perf_trace_enable,

	.disable	= perf_trace_disable,

	.start		= perf_swevent_int,

	.stop		= perf_swevent_void,

	.read		= perf_swevent_read,

	.unthrottle	= perf_swevent_unthrottle,

	.unthrottle	= perf_swevent_void,

};



static int perf_tp_filter_match(struct perf_event *event,

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