* [PATCH] perf/core: do not set cpuctx->cgrp for unscheduled cgroups
@ 2016-10-11 23:27 David Carrillo-Cisneros
2016-11-01 18:52 ` [PATCH v2] " David Carrillo-Cisneros
0 siblings, 1 reply; 4+ messages in thread
From: David Carrillo-Cisneros @ 2016-10-11 23:27 UTC (permalink / raw)
To: linux-kernel
Cc: x86, Ingo Molnar, Thomas Gleixner, Andi Kleen, Kan Liang,
Peter Zijlstra, Vegard Nossum, Paul Turner, Stephane Eranian,
David Carrillo-Cisneros
commit db4a835601b7
("perf/core: Set cgroup in CPU contexts for new cgroup events")
fails to verify that event->cgrp is actually the scheduled cgroup
in a CPU before setting cpuctx->cgrp. This patch fixes that.
The bug only impacts the first cgroup that is created in a CPU.
Now that there is a different path for scheduled and unscheduled
cgroups, add a warning to catch when cpuctx->cgrp is still set after
the last cgroup event has been unsheduled.
Reviewed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
kernel/events/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7c0d263..62f70a3 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -902,6 +902,17 @@ list_update_cgroup_event(struct perf_event *event,
* this will always be called from the right CPU.
*/
cpuctx = __get_cpu_context(ctx);
+
+ /* Only set/clear cpuctx->cgrp if current task uses event->cgrp. */
+ if (perf_cgroup_from_task(current, ctx) != event->cgrp) {
+ /*
+ * We are removing the last cpu event in this context.
+ * If that event is not active in this cpu, cpuctx->cgrp
+ * should've been cleared by perf_cgroup_switch.
+ */
+ WARN_ON_ONCE(!add && cpuctx->cgrp);
+ return;
+ }
cpuctx->cgrp = add ? event->cgrp : NULL;
}
--
2.8.0.rc3.226.g39d4020
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v2] perf/core: do not set cpuctx->cgrp for unscheduled cgroups
2016-10-11 23:27 [PATCH] perf/core: do not set cpuctx->cgrp for unscheduled cgroups David Carrillo-Cisneros
@ 2016-11-01 18:52 ` David Carrillo-Cisneros
2016-11-16 8:36 ` [tip:perf/urgent] perf/core: Do " tip-bot for David Carrillo-Cisneros
0 siblings, 1 reply; 4+ messages in thread
From: David Carrillo-Cisneros @ 2016-11-01 18:52 UTC (permalink / raw)
To: linux-kernel
Cc: x86, Ingo Molnar, Thomas Gleixner, Andi Kleen, Kan Liang,
Nilay Vaish, Peter Zijlstra, Vegard Nossum, Paul Turner,
Stephane Eranian, David Carrillo-Cisneros
(v2 only extends this changelog.)
commit db4a835601b7
("perf/core: Set cgroup in CPU contexts for new cgroup events")
failed to verify that event->cgrp is actually the scheduled cgroup
in a CPU before setting cpuctx->cgrp. This patch fixes that.
Now that there is a different path for scheduled and unscheduled
cgroup, add a warning to catch when cpuctx->cgrp is still set after
the last cgroup event has been unsheduled.
To verify the bug:
# Create 2 cgroups.
mkdir /dev/cgroups/devices/g1
mkdir /dev/cgroups/devices/g2
# launch a task, bind it to a cpu and move it to g1
CPU=2
while :; do : ; done &
P=$!
taskset -pc $CPU $P
echo $P > /dev/cgroups/devices/g1/tasks
# monitor g2 (it runs no tasks) and observe output
perf stat -e cycles -I 1000 -C $CPU -G g2
# time counts unit events
1.000091408 7,579,527 cycles g2
2.000350111 <not counted> cycles g2
3.000589181 <not counted> cycles g2
4.000771428 <not counted> cycles g2
# note first line that displays that a task run in g2, despite
# g2 having no tasks. This is because cpuctx->cgrp was wrongly
# set when context of new event was installed.
# After applying the fix we obtain the right output:
perf stat -e cycles -I 1000 -C $CPU -G g2
# time counts unit events
1.000119615 <not counted> cycles g2
2.000389430 <not counted> cycles g2
3.000590962 <not counted> cycles g2
Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
kernel/events/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index c6e47e9..55953db 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -902,6 +902,17 @@ list_update_cgroup_event(struct perf_event *event,
* this will always be called from the right CPU.
*/
cpuctx = __get_cpu_context(ctx);
+
+ /* Only set/clear cpuctx->cgrp if current task uses event->cgrp. */
+ if (perf_cgroup_from_task(current, ctx) != event->cgrp) {
+ /*
+ * We are removing the last cpu event in this context.
+ * If that event is not active in this cpu, cpuctx->cgrp
+ * should've been cleared by perf_cgroup_switch.
+ */
+ WARN_ON_ONCE(!add && cpuctx->cgrp);
+ return;
+ }
cpuctx->cgrp = add ? event->cgrp : NULL;
}
--
2.8.0.rc3.226.g39d4020
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [tip:perf/urgent] perf/core: Do not set cpuctx->cgrp for unscheduled cgroups
2016-11-01 18:52 ` [PATCH v2] " David Carrillo-Cisneros
@ 2016-11-16 8:36 ` tip-bot for David Carrillo-Cisneros
0 siblings, 0 replies; 4+ messages in thread
From: tip-bot for David Carrillo-Cisneros @ 2016-11-16 8:36 UTC (permalink / raw)
To: linux-tip-commits
Cc: kan.liang, jolsa, pjt, linux-kernel, acme, hpa, peterz,
alexander.shishkin, eranian, torvalds, nilayvaish, vegard.nossum,
mingo, tglx, davidcc
Commit-ID: 864c2357ca898c6171fe5284f5ecc795c8ce27a8
Gitweb: http://git.kernel.org/tip/864c2357ca898c6171fe5284f5ecc795c8ce27a8
Author: David Carrillo-Cisneros <davidcc@google.com>
AuthorDate: Tue, 1 Nov 2016 11:52:58 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 15 Nov 2016 14:18:22 +0100
perf/core: Do not set cpuctx->cgrp for unscheduled cgroups
Commit:
db4a835601b7 ("perf/core: Set cgroup in CPU contexts for new cgroup events")
failed to verify that event->cgrp is actually the scheduled cgroup
in a CPU before setting cpuctx->cgrp. This patch fixes that.
Now that there is a different path for scheduled and unscheduled
cgroup, add a warning to catch when cpuctx->cgrp is still set after
the last cgroup event has been unsheduled.
To verify the bug:
# Create 2 cgroups.
mkdir /dev/cgroups/devices/g1
mkdir /dev/cgroups/devices/g2
# launch a task, bind it to a cpu and move it to g1
CPU=2
while :; do : ; done &
P=$!
taskset -pc $CPU $P
echo $P > /dev/cgroups/devices/g1/tasks
# monitor g2 (it runs no tasks) and observe output
perf stat -e cycles -I 1000 -C $CPU -G g2
# time counts unit events
1.000091408 7,579,527 cycles g2
2.000350111 <not counted> cycles g2
3.000589181 <not counted> cycles g2
4.000771428 <not counted> cycles g2
# note first line that displays that a task run in g2, despite
# g2 having no tasks. This is because cpuctx->cgrp was wrongly
# set when context of new event was installed.
# After applying the fix we obtain the right output:
perf stat -e cycles -I 1000 -C $CPU -G g2
# time counts unit events
1.000119615 <not counted> cycles g2
2.000389430 <not counted> cycles g2
3.000590962 <not counted> cycles g2
Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Link: http://lkml.kernel.org/r/1478026378-86083-1-git-send-email-davidcc@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/events/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0e29213..ff230bb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -902,6 +902,17 @@ list_update_cgroup_event(struct perf_event *event,
* this will always be called from the right CPU.
*/
cpuctx = __get_cpu_context(ctx);
+
+ /* Only set/clear cpuctx->cgrp if current task uses event->cgrp. */
+ if (perf_cgroup_from_task(current, ctx) != event->cgrp) {
+ /*
+ * We are removing the last cpu event in this context.
+ * If that event is not active in this cpu, cpuctx->cgrp
+ * should've been cleared by perf_cgroup_switch.
+ */
+ WARN_ON_ONCE(!add && cpuctx->cgrp);
+ return;
+ }
cpuctx->cgrp = add ? event->cgrp : NULL;
}
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] perf/core: do not set cpuctx->cgrp for unscheduled cgroups
@ 2016-11-16 8:07 David Carrillo-Cisneros
0 siblings, 0 replies; 4+ messages in thread
From: David Carrillo-Cisneros @ 2016-11-16 8:07 UTC (permalink / raw)
To: linux-kernel
Cc: x86, Ingo Molnar, Thomas Gleixner, Andi Kleen, Kan Liang,
Nilay Vaish, Peter Zijlstra, Vegard Nossum, Paul Turner,
Stephane Eranian, David Carrillo-Cisneros
Hi all,
Ping on this patch. Is there any outstanding problem with it?
Hopefully can make it to 4.9
Thanks,
David
^ permalink raw reply [flat|nested] 4+ messages in thread
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2016-11-16 8:36 ` [tip:perf/urgent] perf/core: Do " tip-bot for David Carrillo-Cisneros
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