perf: Fix perf_cgroup_switch for sw-events

commit 95cf59ea72331d0093010543b8951bb43f262cac upstream. Jiri reported that he could trigger the WARN_ON_ONCE() in perf_cgroup_switch() using sw-events. This is because sw-events share a cpuctx with multiple PMUs. Use the ->unique_pmu pointer to limit the pmu iteration to unique cpuctx instances. Change-Id: Id1b5b20f99a6215a6f9532c4a87724302acbde3e Original-Change-Id: Ia478a7650e0286968b9259eb4c87a72b3d95d368 Reported-and-Tested-by: Jiri Olsa <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/n/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Cc: Li Zefan <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
nasty007 · Aug 18, 2017 · a378295 · a378295
1 parent 0f45bad
commit a378295
Showing 1 changed file with 6 additions and 3 deletions.
diff --git a/kernel/events/core.c b/kernel/events/core.c
@@ -377,6 +377,8 @@ void perf_cgroup_switch(struct task_struct *task, int mode)
 
 	list_for_each_entry_rcu(pmu, &pmus, entry) {
 		cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
+		if (cpuctx->unique_pmu != pmu)
+			continue; /* ensure we process each cpuctx once */
 
 		/*
 		 * perf_cgroup_events says at least one
@@ -400,9 +402,10 @@ void perf_cgroup_switch(struct task_struct *task, int mode)
 
 			if (mode & PERF_CGROUP_SWIN) {
 				WARN_ON_ONCE(cpuctx->cgrp);
-				/* set cgrp before ctxsw in to
-				 * allow event_filter_match() to not
-				 * have to pass task around
+				/*
+				 * set cgrp before ctxsw in to allow
+				 * event_filter_match() to not have to pass
+				 * task around
 				 */
 				cpuctx->cgrp = perf_cgroup_from_task(task);
 				cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);