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From: "tip-bot for K.Prasad" <Prasad.Krishnan@gmail.com>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org,
	a.p.zijlstra@chello.nl, Prasad.Krishnan@gmail.com,
	emachado@linux.vnet.ibm.com, fweisbec@gmail.com,
	naveen.n.rao@linux.vnet.ibm.com, tglx@linutronix.de
Subject: [tip:perf/urgent] perf/hwpb: Invoke __perf_event_disable() if interrupts are already disabled
Date: Tue, 4 Sep 2012 11:53:11 -0700	[thread overview]
Message-ID: <tip-500ad2d8b01390c98bc6dce068bccfa9534b8212@git.kernel.org> (raw)
In-Reply-To: <20120802081635.5811.17737.stgit@localhost.localdomain>

Commit-ID:  500ad2d8b01390c98bc6dce068bccfa9534b8212
Gitweb:     http://git.kernel.org/tip/500ad2d8b01390c98bc6dce068bccfa9534b8212
Author:     K.Prasad <Prasad.Krishnan@gmail.com>
AuthorDate: Thu, 2 Aug 2012 13:46:35 +0530
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 4 Sep 2012 17:29:53 +0200

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: Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Signed-off-by: K.Prasad <Prasad.Krishnan@gmail.com>
[naveen.n.rao@linux.vnet.ibm.com: v3: Check to make sure we target current task]
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
---
 include/linux/perf_event.h    |    2 ++
 kernel/events/core.c          |    2 +-
 kernel/events/hw_breakpoint.c |   11 ++++++++++-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index ad04dfc..33ed9d6 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -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
 
diff --git a/kernel/events/core.c b/kernel/events/core.c
index efef428..7fee567 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -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;
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index bb38c4d..9a7b487 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -453,7 +453,16 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att
 	int old_type = bp->attr.bp_type;
 	int err = 0;
 
-	perf_event_disable(bp);
+	/*
+	 * 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;
 	bp->attr.bp_type = attr->bp_type;

      parent reply	other threads:[~2012-09-04 18:53 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-11  6:02 [Patch][perf] Invoke __perf_event_disable without an IPI K.Prasad
2012-06-11 11:13 ` Peter Zijlstra
2012-06-12  6:06   ` K.Prasad
2012-06-12  9:12     ` Peter Zijlstra
2012-07-06  9:52       ` [PATCH v2] Hardware breakpoints: Invoke __perf_event_disable() if interrupts are already disabled Naveen N. Rao
2012-07-06 10:18         ` Naveen N. Rao
2012-07-18 10:30           ` [PATCH v2 RESEND] " Naveen N. Rao
2012-07-18 11:57             ` Frederic Weisbecker
2012-07-19 11:16               ` Naveen N. Rao
2012-07-25 11:32                 ` Naveen N. Rao
2012-07-31 13:41                   ` Frederic Weisbecker
2012-08-02  8:16                     ` [PATCH v3] " Naveen N. Rao
2012-08-15 17:37                       ` Naveen N. Rao
2012-08-15 18:42                         ` Frederic Weisbecker
2012-08-16  8:16                           ` Peter Zijlstra
2012-08-29  2:45                             ` Naveen N. Rao
2012-09-04 18:53                       ` tip-bot for K.Prasad [this message]

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