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Commit 96f6d444 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: avoid recursion 



Tracepoint events like lock_acquire and software counters like
pagefaults can recurse into the perf counter code again, avoid that.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.152096433@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f4a2deb4

include/linux/perf_counter.h

+7 −0
Original line number Diff line number Diff line
@@ -328,6 +328,13 @@ struct perf_cpu_context { 
	int				active_oncpu;

	int				max_pertask;

	int				exclusive;



	/*

	 * Recursion avoidance:

	 *

	 * task, softirq, irq, nmi context

	 */

	int			recursion[4];

};



/*

kernel/perf_counter.c

+26 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/mm.h>

#include <linux/vmstat.h>

#include <linux/rculist.h>

#include <linux/hardirq.h>



#include <asm/irq_regs.h>
@@ -1532,10 +1533,31 @@ static void perf_swcounter_ctx_event(struct perf_counter_context *ctx, 
	rcu_read_unlock();

}



static int *perf_swcounter_recursion_context(struct perf_cpu_context *cpuctx)

{

	if (in_nmi())

		return &cpuctx->recursion[3];



	if (in_irq())

		return &cpuctx->recursion[2];



	if (in_softirq())

		return &cpuctx->recursion[1];



	return &cpuctx->recursion[0];

}



static void __perf_swcounter_event(enum perf_event_types type, u32 event,

				   u64 nr, int nmi, struct pt_regs *regs)

{

	struct perf_cpu_context *cpuctx = &get_cpu_var(perf_cpu_context);

	int *recursion = perf_swcounter_recursion_context(cpuctx);



	if (*recursion)

		goto out;



	(*recursion)++;

	barrier();



	perf_swcounter_ctx_event(&cpuctx->ctx, type, event, nr, nmi, regs);

	if (cpuctx->task_ctx) {
@@ -1543,6 +1565,10 @@ static void __perf_swcounter_event(enum perf_event_types type, u32 event, 
				nr, nmi, regs);

	}



	barrier();

	(*recursion)--;



out:

	put_cpu_var(perf_cpu_context);

}