[PATCH v2 0/2] perf kvm stat live: Copy events

[PATCH v2 0/2] perf kvm stat live: Copy events

[Alexander Yarygin]

Hello,

This is a fix of 'perf kvm stat live' crash when it tries
to parse events that have been already overwritten by the kernel.

Patches
- 1/2 adds an option to copy events when they are pushed to the samples queue.  The patch is based on the patch by David Ahern (https://lkml.org/lkml/2013/9/6/388)
- 2/2 enables the copying for perf kvm stat live.

Changes in v2:
  - the option to copy events is now a part of ordered_events
  - use memdup() instead malloc()/memcpy()
  - events alocations are under the report.queue-size limit

Previous thread: https://lkml.org/lkml/2014/9/18/353

Thanks!

Alexander Yarygin (2):
  perf tools: Add option to copy events when queueing
  perf kvm stat live: Enable events copying

 tools/perf/builtin-kvm.c         |  1 +
 tools/perf/util/ordered-events.c | 41 ++++++++++++++++++++++++++++++++++++----
 tools/perf/util/ordered-events.h | 10 +++++++++-
 tools/perf/util/session.c        |  5 ++---
 4 files changed, 49 insertions(+), 8 deletions(-)

-- 
1.9.1

[PATCH 1/2] perf tools: Add option to copy events when queueing

[Alexander Yarygin]

From: David Ahern <dsahern@gmail.com>

When processing events the session code has an ordered samples queue which is
used to time-sort events coming in across multiple mmaps. At a later point in
time samples on the queue are flushed up to some timestamp at which point the
event is actually processed.

When analyzing events live (ie., record/analysis path in the same command)
there is a race that leads to corrupted events and parse errors which cause
perf to terminate. The problem is that when the event is placed in the ordered
samples queue it is only a reference to the event which is really sitting in
the mmap buffer. Even though the event is queued for later processing the mmap
tail pointer is updated which indicates to the kernel that the event has been
processed. The race is flushing the event from the queue before it gets
overwritten by some other event. For commands trying to process events live
(versus just writing to a file) and processing a high rate of events this leads
to parse failures and perf terminates.

Examples hitting this problem are 'perf kvm stat live', especially with nested
VMs which generate 100,000+ traces per second, and a command processing
scheduling events with a high rate of context switching -- e.g., running
'perf bench sched pipe'.

This patch offers live commands an option to copy the event when it is placed in
the ordered samples queue.

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
---
 tools/perf/util/ordered-events.c | 41 ++++++++++++++++++++++++++++++++++++----
 tools/perf/util/ordered-events.h | 10 +++++++++-
 tools/perf/util/session.c        |  5 ++---
 3 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index 706ce1a..f7383cc 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -1,5 +1,6 @@
 #include <linux/list.h>
 #include <linux/compiler.h>
+#include <linux/string.h>
 #include "ordered-events.h"
 #include "evlist.h"
 #include "session.h"
@@ -58,10 +59,24 @@ static void queue_event(struct ordered_events *oe, struct ordered_event *new)
 }
 
 #define MAX_SAMPLE_BUFFER	(64 * 1024 / sizeof(struct ordered_event))
-static struct ordered_event *alloc_event(struct ordered_events *oe)
+static struct ordered_event *alloc_event(struct ordered_events *oe,
+					 union perf_event *event)
 {
 	struct list_head *cache = &oe->cache;
 	struct ordered_event *new = NULL;
+	union perf_event *new_event = NULL;
+
+	if (oe->copy_on_queue) {
+		if (oe->cur_alloc_size < oe->max_alloc_size) {
+			new_event = memdup(event, event->header.size);
+			if (new_event)
+				oe->cur_alloc_size += event->header.size;
+		}
+	} else
+		new_event = event;
+
+	if (!new_event)
+		return NULL;
 
 	if (!list_empty(cache)) {
 		new = list_entry(cache->next, struct ordered_event, list);
@@ -74,8 +89,13 @@ static struct ordered_event *alloc_event(struct ordered_events *oe)
 		size_t size = MAX_SAMPLE_BUFFER * sizeof(*new);
 
 		oe->buffer = malloc(size);
-		if (!oe->buffer)
+		if (!oe->buffer) {
+			if (oe->copy_on_queue) {
+				oe->cur_alloc_size -= new_event->header.size;
+				free(new_event);
+			}
 			return NULL;
+		}
 
 		pr("alloc size %" PRIu64 "B (+%zu), max %" PRIu64 "B\n",
 		   oe->cur_alloc_size, size, oe->max_alloc_size);
@@ -90,15 +110,19 @@ static struct ordered_event *alloc_event(struct ordered_events *oe)
 		pr("allocation limit reached %" PRIu64 "B\n", oe->max_alloc_size);
 	}
 
+	new->event = new_event;
+
 	return new;
 }
 
 struct ordered_event *
-ordered_events__new(struct ordered_events *oe, u64 timestamp)
+ordered_events__new(struct ordered_events *oe, u64 timestamp,
+		    union perf_event *event)
 {
 	struct ordered_event *new;
 
-	new = alloc_event(oe);
+	new = alloc_event(oe, event);
+
 	if (new) {
 		new->timestamp = timestamp;
 		queue_event(oe, new);
@@ -111,6 +135,10 @@ void ordered_events__delete(struct ordered_events *oe, struct ordered_event *eve
 {
 	list_move(&event->list, &oe->cache);
 	oe->nr_events--;
+	if (oe->copy_on_queue) {
+		oe->cur_alloc_size -= event->event->header.size;
+		free(event->event);
+	}
 }
 
 static int __ordered_events__flush(struct perf_session *s,
@@ -240,6 +268,11 @@ void ordered_events__free(struct ordered_events *oe)
 
 		event = list_entry(oe->to_free.next, struct ordered_event, list);
 		list_del(&event->list);
+		if (oe->copy_on_queue) {
+			oe->cur_alloc_size -= event->event->header.size;
+			free(event->event);
+		}
+
 		free(event);
 	}
 }
diff --git a/tools/perf/util/ordered-events.h b/tools/perf/util/ordered-events.h
index 3b2f205..7b8f9b0 100644
--- a/tools/perf/util/ordered-events.h
+++ b/tools/perf/util/ordered-events.h
@@ -34,9 +34,11 @@ struct ordered_events {
 	int			buffer_idx;
 	unsigned int		nr_events;
 	enum oe_flush		last_flush_type;
+	bool                    copy_on_queue;
 };
 
-struct ordered_event *ordered_events__new(struct ordered_events *oe, u64 timestamp);
+struct ordered_event *ordered_events__new(struct ordered_events *oe, u64 timestamp,
+					  union perf_event *event);
 void ordered_events__delete(struct ordered_events *oe, struct ordered_event *event);
 int ordered_events__flush(struct perf_session *s, struct perf_tool *tool,
 			  enum oe_flush how);
@@ -48,4 +50,10 @@ void ordered_events__set_alloc_size(struct ordered_events *oe, u64 size)
 {
 	oe->max_alloc_size = size;
 }
+
+static inline
+void ordered_events__set_copy_on_queue(struct ordered_events *oe, bool copy)
+{
+	oe->copy_on_queue = copy;
+}
 #endif /* __ORDERED_EVENTS_H */
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 6d2d50d..976064d 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -532,17 +532,16 @@ int perf_session_queue_event(struct perf_session *s, union perf_event *event,
 			return -EINVAL;
 	}
 
-	new = ordered_events__new(oe, timestamp);
+	new = ordered_events__new(oe, timestamp, event);
 	if (!new) {
 		ordered_events__flush(s, tool, OE_FLUSH__HALF);
-		new = ordered_events__new(oe, timestamp);
+		new = ordered_events__new(oe, timestamp, event);
 	}
 
 	if (!new)
 		return -ENOMEM;
 
 	new->file_offset = file_offset;
-	new->event = event;
 	return 0;
 }
 
-- 
1.9.1

Re: [PATCH 1/2] perf tools: Add option to copy events when queueing

[Jiri Olsa]

On Thu, Oct 02, 2014 at 02:32:08PM +0400, Alexander Yarygin wrote:

SNIP

> +		if (!oe->buffer) {
> +			if (oe->copy_on_queue) {
> +				oe->cur_alloc_size -= new_event->header.size;
> +				free(new_event);
> +			}
>  			return NULL;
> +		}
>  
>  		pr("alloc size %" PRIu64 "B (+%zu), max %" PRIu64 "B\n",
>  		   oe->cur_alloc_size, size, oe->max_alloc_size);
> @@ -90,15 +110,19 @@ static struct ordered_event *alloc_event(struct ordered_events *oe)
>  		pr("allocation limit reached %" PRIu64 "B\n", oe->max_alloc_size);
>  	}
>  
> +	new->event = new_event;
> +
>  	return new;
>  }
>  
>  struct ordered_event *
> -ordered_events__new(struct ordered_events *oe, u64 timestamp)
> +ordered_events__new(struct ordered_events *oe, u64 timestamp,
> +		    union perf_event *event)
>  {
>  	struct ordered_event *new;
>  
> -	new = alloc_event(oe);
> +	new = alloc_event(oe, event);
> +
>  	if (new) {
>  		new->timestamp = timestamp;
>  		queue_event(oe, new);
> @@ -111,6 +135,10 @@ void ordered_events__delete(struct ordered_events *oe, struct ordered_event *eve
>  {
>  	list_move(&event->list, &oe->cache);
>  	oe->nr_events--;
> +	if (oe->copy_on_queue) {
> +		oe->cur_alloc_size -= event->event->header.size;
> +		free(event->event);
> +	}
>  }
>  
>  static int __ordered_events__flush(struct perf_session *s,
> @@ -240,6 +268,11 @@ void ordered_events__free(struct ordered_events *oe)
>  
>  		event = list_entry(oe->to_free.next, struct ordered_event, list);
>  		list_del(&event->list);
> +		if (oe->copy_on_queue) {
> +			oe->cur_alloc_size -= event->event->header.size;
> +			free(event->event);
> +		}
> +
>  		free(event);

looks ok.. but I was wondering if we could move those repeating
bits in function.. something like below (untested, just compiled)

thanks,
jirka


---
diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
index f7383ccc6690..583dcefc92fb 100644
--- a/tools/perf/util/ordered-events.c
+++ b/tools/perf/util/ordered-events.c
@@ -58,23 +58,41 @@ static void queue_event(struct ordered_events *oe, struct ordered_event *new)
 	}
 }
 
+static union perf_event *__dup_event(struct ordered_events *oe, union perf_event *event)
+{
+	union perf_event *new_event = NULL;
+
+	if (oe->cur_alloc_size < oe->max_alloc_size) {
+		new_event = memdup(event, event->header.size);
+		if (new_event)
+			oe->cur_alloc_size += event->header.size;
+	}
+
+	return new_event;
+}
+
+static union perf_event *dup_event(struct ordered_events *oe, union perf_event *event)
+{
+	return oe->copy_on_queue ? __dup_event(oe, event) : event;
+}
+
+static void free_dup_event(struct ordered_events *oe, union perf_event *event)
+{
+	if (oe->copy_on_queue) {
+		oe->cur_alloc_size -= event->header.size;
+		free(event);
+	}
+}
+
 #define MAX_SAMPLE_BUFFER	(64 * 1024 / sizeof(struct ordered_event))
 static struct ordered_event *alloc_event(struct ordered_events *oe,
 					 union perf_event *event)
 {
 	struct list_head *cache = &oe->cache;
 	struct ordered_event *new = NULL;
-	union perf_event *new_event = NULL;
-
-	if (oe->copy_on_queue) {
-		if (oe->cur_alloc_size < oe->max_alloc_size) {
-			new_event = memdup(event, event->header.size);
-			if (new_event)
-				oe->cur_alloc_size += event->header.size;
-		}
-	} else
-		new_event = event;
+	union perf_event *new_event;
 
+	new_event = dup_event(oe, event);
 	if (!new_event)
 		return NULL;
 
@@ -90,10 +108,7 @@ static struct ordered_event *alloc_event(struct ordered_events *oe,
 
 		oe->buffer = malloc(size);
 		if (!oe->buffer) {
-			if (oe->copy_on_queue) {
-				oe->cur_alloc_size -= new_event->header.size;
-				free(new_event);
-			}
+			free_dup_event(oe, new_event);
 			return NULL;
 		}
 
@@ -135,10 +150,7 @@ void ordered_events__delete(struct ordered_events *oe, struct ordered_event *eve
 {
 	list_move(&event->list, &oe->cache);
 	oe->nr_events--;
-	if (oe->copy_on_queue) {
-		oe->cur_alloc_size -= event->event->header.size;
-		free(event->event);
-	}
+	free_dup_event(oe, event->event);
 }
 
 static int __ordered_events__flush(struct perf_session *s,
@@ -268,11 +280,7 @@ void ordered_events__free(struct ordered_events *oe)
 
 		event = list_entry(oe->to_free.next, struct ordered_event, list);
 		list_del(&event->list);
-		if (oe->copy_on_queue) {
-			oe->cur_alloc_size -= event->event->header.size;
-			free(event->event);
-		}
-
+		free_dup_event(oe, event->event);
 		free(event);
 	}
 }

Re: [PATCH 1/2] perf tools: Add option to copy events when queueing

[Alexander Yarygin]

Jiri Olsa <jolsa@redhat.com> writes:

[..]

>
> looks ok.. but I was wondering if we could move those repeating
> bits in function.. something like below (untested, just compiled)
>
> thanks,
> jirka
>
>

[..]

Yep, it's better. Just checked - it works. How should we process?

Thanks.

Re: [PATCH 1/2] perf tools: Add option to copy events when queueing

[Jiri Olsa]

On Thu, Oct 02, 2014 at 07:21:58PM +0400, Alexander Yarygin wrote:
> Jiri Olsa <jolsa@redhat.com> writes:
> 
> [..]
> 
> >
> > looks ok.. but I was wondering if we could move those repeating
> > bits in function.. something like below (untested, just compiled)
> >
> > thanks,
> > jirka
> >
> >
> 
> [..]
> 
> Yep, it's better. Just checked - it works. How should we process?

just update your patch with that change and resend

thanks,
jirka

Re: [PATCH 1/2] perf tools: Add option to copy events when queueing

[David Ahern]

On 10/2/14, 4:32 AM, Alexander Yarygin wrote:
> From: David Ahern <dsahern@gmail.com>

At this point the patch is no longer from me. You have done the 
migration to ordered_events. You can change that to based on a patch 
from ...

[PATCH 2/2] perf kvm stat live: Enable events copying

[Alexander Yarygin]

Process of analyzing events caused by 2 functions: mmap_read() and
finished_round().
During mmap_read(), perf receives events from shared memory, queues
their pointers for further processing in finished_round() and notifies
the kernel that the events have been processed.
By the time when finished_round() is invoked, queued events can be
overwritten by the kernel, so the finished_round() occurs on potentially
corrupted memory.

Since there is no place where the event can be safely consumed,
let's copy events when queueing.

Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 tools/perf/builtin-kvm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index f5d3ae4..80efbfa 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -1370,6 +1370,7 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,
 	}
 	kvm->session->evlist = kvm->evlist;
 	perf_session__set_id_hdr_size(kvm->session);
+	ordered_events__set_copy_on_queue(&kvm->session->ordered_events, true);
 	machine__synthesize_threads(&kvm->session->machines.host, &kvm->opts.target,
 				    kvm->evlist->threads, false);
 	err = kvm_live_open_events(kvm);
-- 
1.9.1

[PATCH v4 0/2] perf kvm stat live: Copy events

[Alexander Yarygin]

Hello,

This is a fix of 'perf kvm stat live' crash when it tries
to parse events that have been already overwritten by the kernel.

Patches
- 1/2 adds an option to copy events when they are pushed to the samples queue.  The patch is based on the patch by David Ahern (https://lkml.org/lkml/2013/9/6/388)
- 2/2 enables the copying for perf kvm stat live.

Changes in v4:
  - removed extra whitespaces :)

Changes in v3:
  - move repetitive code into functions

Changes in v2:
  - the option to copy events is now a part of ordered_events
  - use memdup() instead malloc()/memcpy()
  - events alocations are under the report.queue-size limit

Alexander Yarygin (2):
  perf tools: Add option to copy events when queueing
  perf kvm stat live: Enable events copying

 tools/perf/builtin-kvm.c         |  1 +
 tools/perf/util/ordered-events.c | 49 ++++++++++++++++++++++++++++++++++++----
 tools/perf/util/ordered-events.h | 10 +++++++-
 tools/perf/util/session.c        |  5 ++--
 4 files changed, 57 insertions(+), 8 deletions(-)

-- 
1.9.1

[PATCH 2/2] perf kvm stat live: Enable events copying

[Alexander Yarygin]

Process of analyzing events caused by 2 functions: mmap_read() and
finished_round().
During mmap_read(), perf receives events from shared memory, queues
their pointers for further processing in finished_round() and notifies
the kernel that the events have been processed.
By the time when finished_round() is invoked, queued events can be
overwritten by the kernel, so the finished_round() occurs on potentially
corrupted memory.

Since there is no place where the event can be safely consumed,
let's copy events when queueing.

Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 tools/perf/builtin-kvm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index f5d3ae4..80efbfa 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -1370,6 +1370,7 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,
 	}
 	kvm->session->evlist = kvm->evlist;
 	perf_session__set_id_hdr_size(kvm->session);
+	ordered_events__set_copy_on_queue(&kvm->session->ordered_events, true);
 	machine__synthesize_threads(&kvm->session->machines.host, &kvm->opts.target,
 				    kvm->evlist->threads, false);
 	err = kvm_live_open_events(kvm);
-- 
1.9.1

[PATCH v3 0/2] perf kvm stat live: Copy events

[Alexander Yarygin]

Hello,

This is a fix of 'perf kvm stat live' crash when it tries
to parse events that have been already overwritten by the kernel.

Patches
- 1/2 adds an option to copy events when they are pushed to the samples queue.  The patch is based on the patch by David Ahern (https://lkml.org/lkml/2013/9/6/388)
- 2/2 enables the copying for perf kvm stat live.

Changes in v3:
  - move repetitive code into functions

Changes in v2:
  - the option to copy events is now a part of ordered_events
  - use memdup() instead malloc()/memcpy()
  - events alocations are under the report.queue-size limit

Alexander Yarygin (2):
  perf tools: Add option to copy events when queueing
  perf kvm stat live: Enable events copying

 tools/perf/builtin-kvm.c         |  1 +
 tools/perf/util/ordered-events.c | 49 ++++++++++++++++++++++++++++++++++++----
 tools/perf/util/ordered-events.h | 10 +++++++-
 tools/perf/util/session.c        |  5 ++--
 4 files changed, 57 insertions(+), 8 deletions(-)

-- 
1.9.1

[PATCH 2/2] perf kvm stat live: Enable events copying

[Alexander Yarygin]

Process of analyzing events caused by 2 functions: mmap_read() and
finished_round().
During mmap_read(), perf receives events from shared memory, queues
their pointers for further processing in finished_round() and notifies
the kernel that the events have been processed.
By the time when finished_round() is invoked, queued events can be
overwritten by the kernel, so the finished_round() occurs on potentially
corrupted memory.

Since there is no place where the event can be safely consumed,
let's copy events when queueing.

Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 tools/perf/builtin-kvm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index f5d3ae4..80efbfa 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -1370,6 +1370,7 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,
 	}
 	kvm->session->evlist = kvm->evlist;
 	perf_session__set_id_hdr_size(kvm->session);
+	ordered_events__set_copy_on_queue(&kvm->session->ordered_events, true);
 	machine__synthesize_threads(&kvm->session->machines.host, &kvm->opts.target,
 				    kvm->evlist->threads, false);
 	err = kvm_live_open_events(kvm);
-- 
1.9.1

[PATCH 0/2] perf kvm stat live: Copy events

[Alexander Yarygin]

Hello,

This is a second attempt to fix 'perf kvm stat live' crash when it tries
to parse events that have been already overwritten by the kernel.
Previous thread: https://lkml.org/lkml/2014/9/12/450

Patches
- 1/2 is patch by David Ahern (https://lkml.org/lkml/2013/9/6/388)
  rebased to the current upstream (hope I did it right). It adds an option
  to copy events when they are pushed to the samples queue.
- 2/2 enables the copying for perf kvm stat live.

Looks like we have to live with possibility to get thousands malloc()s/free()s
per second...

Alexander Yarygin (2):
  perf session: Add option to copy events when queueing
  perf kvm stat live: Enable events copying

 tools/perf/builtin-kvm.c         |  1 +
 tools/perf/util/ordered-events.c | 12 +++++++++---
 tools/perf/util/ordered-events.h |  2 +-
 tools/perf/util/session.c        | 12 +++++++++---
 tools/perf/util/session.h        |  1 +
 5 files changed, 21 insertions(+), 7 deletions(-)

-- 
1.9.1

[PATCH 2/2] perf kvm stat live: Enable events copying

[Alexander Yarygin]

Process of analyzing events caused by 2 functions: mmap_read() and
finished_round().
During mmap_read(), perf receives events from shared memory, queues
their pointers for further processing in finished_round() and notifies
the kernel that the events have been processed.
By the time when finished_round() is invoked, queued events can be
overwritten by the kernel, so the finished_round() occurs on potentially
corrupted memory.

Let's copy events when queueing.

Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 tools/perf/builtin-kvm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index f5d3ae4..c5b6d1d 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -1369,6 +1369,7 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,
 		goto out;
 	}
 	kvm->session->evlist = kvm->evlist;
+	kvm->session->copy_on_queue = true;
 	perf_session__set_id_hdr_size(kvm->session);
 	machine__synthesize_threads(&kvm->session->machines.host, &kvm->opts.target,
 				    kvm->evlist->threads, false);
-- 
1.9.1