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Commit 500ad2d8 authored by K.Prasad's avatar K.Prasad Committed by Ingo Molnar
Browse files

perf/hwpb: Invoke __perf_event_disable() if interrupts are already disabled 



While debugging a warning message on PowerPC while using hardware
breakpoints, it was discovered that when perf_event_disable is invoked
through hw_breakpoint_handler function with interrupts disabled, a
subsequent IPI in the code path would trigger a WARN_ON_ONCE message in
smp_call_function_single function.

This patch calls __perf_event_disable() when interrupts are already
disabled, instead of perf_event_disable().

Reported-by: default avatarEdjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Signed-off-by: default avatarK.Prasad <Prasad.Krishnan@gmail.com>
[naveen.n.rao@linux.vnet.ibm.com: v3: Check to make sure we target current task]
Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120802081635.5811.17737.stgit@localhost.localdomain


[ Fixed build error on MIPS. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3ec18cd8

include/linux/perf_event.h

+2 −0
Original line number Diff line number Diff line
@@ -1296,6 +1296,7 @@ extern int perf_swevent_get_recursion_context(void); 
extern void perf_swevent_put_recursion_context(int rctx);

extern void perf_event_enable(struct perf_event *event);

extern void perf_event_disable(struct perf_event *event);

extern int __perf_event_disable(void *info);

extern void perf_event_task_tick(void);

#else

static inline void
@@ -1334,6 +1335,7 @@ static inline int perf_swevent_get_recursion_context(void) { return -1; } 
static inline void perf_swevent_put_recursion_context(int rctx)		{ }

static inline void perf_event_enable(struct perf_event *event)		{ }

static inline void perf_event_disable(struct perf_event *event)		{ }

static inline int __perf_event_disable(void *info)			{ return -1; }

static inline void perf_event_task_tick(void)				{ }

#endif

kernel/events/core.c

+1 −1
Original line number Diff line number Diff line
@@ -1253,7 +1253,7 @@ retry: 
/*

 * Cross CPU call to disable a performance event

 */

static int __perf_event_disable(void *info)

int __perf_event_disable(void *info)

{

	struct perf_event *event = info;

	struct perf_event_context *ctx = event->ctx;

kernel/events/hw_breakpoint.c

+10 −1
Original line number Diff line number Diff line
@@ -453,6 +453,15 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att 
	int old_type = bp->attr.bp_type;

	int err = 0;



	/*

	 * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it

	 * will not be possible to raise IPIs that invoke __perf_event_disable.

	 * So call the function directly after making sure we are targeting the

	 * current task.

	 */

	if (irqs_disabled() && bp->ctx && bp->ctx->task == current)

		__perf_event_disable(bp);

	else

		perf_event_disable(bp);



	bp->attr.bp_addr = attr->bp_addr;