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Patch "perf/x86/intel/bts: Fix DS area sharing with x86_pmu events" has been added to the 4.1-stable tree

PATCH [email protected] 1 participant 1 message Jun 26, 2015

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This is a note to let you know that I've just added the patch titled

perf/x86/intel/bts: Fix DS area sharing with x86_pmu events

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-x86-intel-bts-fix-ds-area-sharing-with-x86_pmu-events.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 6b099d9b040b0f3d0aec05b560d7caf879af5077 Mon Sep 17 00:00:00 2001

From: Alexander Shishkin <[email protected]>
Date: Thu, 11 Jun 2015 15:13:56 +0300
Subject: perf/x86/intel/bts: Fix DS area sharing with x86_pmu events

From: Alexander Shishkin <[email protected]>

commit 6b099d9b040b0f3d0aec05b560d7caf879af5077 upstream.

Currently, the intel_bts driver relies on the DS area allocated by the x86_pmu code in its event_init() path, which is a bug: creating a BTS event while no x86_pmu events are present results in a NULL pointer dereference.

The same DS area is also used by PEBS sampling, which makes it quite a bit trickier to have a separate one for intel_bts' purposes.

This patch makes intel_bts driver use the same DS allocation and reference counting code as x86_pmu to make sure it is always present when either intel_bts or x86_pmu need it.

Signed-off-by Alexander Shishkin <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Cc Andrew Morton <[email protected]>
Cc Andy Lutomirski <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Brian Gerst <[email protected]>
Cc Denys Vlasenko <[email protected]>
Cc H. Peter Anvin <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Oleg Nesterov <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc [email protected]
Cc [email protected]
Link http://lkml.kernel.org/r/1434024837-9916-2-git-send-email-alexander.shishkin@linux.intel.com open here
Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 arch/x86/kernel/cpu/perf_event.c           |   52 ++++++++++++++++++-----------
 arch/x86/kernel/cpu/perf_event.h           |    4 ++
 arch/x86/kernel/cpu/perf_event_intel_bts.c |    9 +++++
 3 files changed, 46 insertions(+), 19 deletions(-)
arch/x86/kernel/cpu/perf_event.c +33 -19
@@ -270,11 +270,7 @@ msr_fail:
 
 static void hw_perf_event_destroy(struct perf_event *event)
 {
-	if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {
-		release_pmc_hardware();
-		release_ds_buffers();
-		mutex_unlock(&pmc_reserve_mutex);
-	}
+	x86_release_hardware();
 }
 
 void hw_perf_lbr_event_destroy(struct perf_event *event)

@@ -324,6 +320,35 @@ set_ext_hw_attr(struct hw_perf_event *hw
 	return x86_pmu_extra_regs(val, event);
 }
 
+int x86_reserve_hardware(void)
+{
+	int err = 0;
+
+	if (!atomic_inc_not_zero(&active_events)) {
+		mutex_lock(&pmc_reserve_mutex);
+		if (atomic_read(&active_events) == 0) {
+			if (!reserve_pmc_hardware())
+				err = -EBUSY;
+			else
+				reserve_ds_buffers();
+		}
+		if (!err)
+			atomic_inc(&active_events);
+		mutex_unlock(&pmc_reserve_mutex);
+	}
+
+	return err;
+}
+
+void x86_release_hardware(void)
+{
+	if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {
+		release_pmc_hardware();
+		release_ds_buffers();
+		mutex_unlock(&pmc_reserve_mutex);
+	}
+}
+
 /*
  * Check if we can create event of a certain type (that no conflicting events
  * are present).

@@ -336,9 +361,10 @@ int x86_add_exclusive(unsigned int what)
 		return 0;
 
 	mutex_lock(&pmc_reserve_mutex);
-	for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++)
+	for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++) {
 		if (i != what && atomic_read(&x86_pmu.lbr_exclusive[i]))
 			goto out;
+	}
 
 	atomic_inc(&x86_pmu.lbr_exclusive[what]);
 	ret = 0;

@@ -527,19 +553,7 @@ static int __x86_pmu_event_init(struct p
 	if (!x86_pmu_initialized())
 		return -ENODEV;
 
-	err = 0;
-	if (!atomic_inc_not_zero(&active_events)) {
-		mutex_lock(&pmc_reserve_mutex);
-		if (atomic_read(&active_events) == 0) {
-			if (!reserve_pmc_hardware())
-				err = -EBUSY;
-			else
-				reserve_ds_buffers();
-		}
-		if (!err)
-			atomic_inc(&active_events);
-		mutex_unlock(&pmc_reserve_mutex);
-	}
+	err = x86_reserve_hardware();
 	if (err)
 		return err;
arch/x86/kernel/cpu/perf_event.h +4 -0
@@ -703,6 +703,10 @@ int x86_add_exclusive(unsigned int what)
 
 void x86_del_exclusive(unsigned int what);
 
+int x86_reserve_hardware(void);
+
+void x86_release_hardware(void);
+
 void hw_perf_lbr_event_destroy(struct perf_event *event);
 
 int x86_setup_perfctr(struct perf_event *event);
arch/x86/kernel/cpu/perf_event_intel_bts.c +9 -0
@@ -483,17 +483,26 @@ static int bts_event_add(struct perf_eve
 
 static void bts_event_destroy(struct perf_event *event)
 {
+	x86_release_hardware();
 	x86_del_exclusive(x86_lbr_exclusive_bts);
 }
 
 static int bts_event_init(struct perf_event *event)
 {
+	int ret;
+
 	if (event->attr.type != bts_pmu.type)
 		return -ENOENT;
 
 	if (x86_add_exclusive(x86_lbr_exclusive_bts))
 		return -EBUSY;
 
+	ret = x86_reserve_hardware();
+	if (ret) {
+		x86_del_exclusive(x86_lbr_exclusive_bts);
+		return ret;
+	}
+
 	event->destroy = bts_event_destroy;
 
 	return 0;

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/perf-x86-intel-bts-fix-ds-area-sharing-with-x86_pmu-events.patch queue-4.1/perf-fix-ring_buffer_attach-rcu-sync-again.patch