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Commit 614e4c4e authored by Stephane Eranian's avatar Stephane Eranian Committed by Ingo Molnar
Browse files

perf/core: Robustify the perf_cgroup_from_task() RCU checks 



This patch reinforces the lockdep checks performed by
perf_cgroup_from_tsk() by passing the perf_event_context
whenever possible. It is okay to not hold the RCU read lock
when we know we hold the ctx->lock. This patch makes sure this
property holds.

In some functions, such as perf_cgroup_sched_in(), we do not
pass the context because we are sure we are holding the RCU
read lock.

Signed-off-by: default avatarStephane Eranian <eranian@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: edumazet@google.com
Link: http://lkml.kernel.org/r/1447322404-10920-3-git-send-email-eranian@google.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ddaaf4e2

arch/x86/kernel/cpu/perf_event_intel_cqm.c

+1 −1
Original line number Diff line number Diff line
@@ -298,7 +298,7 @@ static bool __match_event(struct perf_event *a, struct perf_event *b) 
static inline struct perf_cgroup *event_to_cgroup(struct perf_event *event)

{

	if (event->attach_state & PERF_ATTACH_TASK)

		return perf_cgroup_from_task(event->hw.target);

		return perf_cgroup_from_task(event->hw.target, event->ctx);



	return event->cgrp;

}

include/linux/perf_event.h

+4 −2
Original line number Diff line number Diff line
@@ -697,9 +697,11 @@ struct perf_cgroup { 
 * if there is no cgroup event for the current CPU context.

 */

static inline struct perf_cgroup *

perf_cgroup_from_task(struct task_struct *task)

perf_cgroup_from_task(struct task_struct *task, struct perf_event_context *ctx)

{

	return container_of(task_css(task, perf_event_cgrp_id),

	return container_of(task_css_check(task, perf_event_cgrp_id,

					   ctx ? lockdep_is_held(&ctx->lock)

					       : true),

			    struct perf_cgroup, css);

}

#endif /* CONFIG_CGROUP_PERF */

kernel/events/core.c

+13 −7
Original line number Diff line number Diff line
@@ -435,7 +435,7 @@ static inline void update_cgrp_time_from_event(struct perf_event *event) 
	if (!is_cgroup_event(event))

		return;



	cgrp = perf_cgroup_from_task(current);

	cgrp = perf_cgroup_from_task(current, event->ctx);

	/*

	 * Do not update time when cgroup is not active

	 */
@@ -458,7 +458,7 @@ perf_cgroup_set_timestamp(struct task_struct *task, 
	if (!task || !ctx->nr_cgroups)

		return;



	cgrp = perf_cgroup_from_task(task);

	cgrp = perf_cgroup_from_task(task, ctx);

	info = this_cpu_ptr(cgrp->info);

	info->timestamp = ctx->timestamp;

}
@@ -521,8 +521,10 @@ static void perf_cgroup_switch(struct task_struct *task, int mode) 
				 * set cgrp before ctxsw in to allow

				 * event_filter_match() to not have to pass

				 * task around

				 * we pass the cpuctx->ctx to perf_cgroup_from_task()

				 * because cgorup events are only per-cpu

				 */

				cpuctx->cgrp = perf_cgroup_from_task(task);

				cpuctx->cgrp = perf_cgroup_from_task(task, &cpuctx->ctx);

				cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);

			}

			perf_pmu_enable(cpuctx->ctx.pmu);
@@ -542,15 +544,17 @@ static inline void perf_cgroup_sched_out(struct task_struct *task, 
	rcu_read_lock();

	/*

	 * we come here when we know perf_cgroup_events > 0

	 * we do not need to pass the ctx here because we know

	 * we are holding the rcu lock

	 */

	cgrp1 = perf_cgroup_from_task(task);

	cgrp1 = perf_cgroup_from_task(task, NULL);



	/*

	 * next is NULL when called from perf_event_enable_on_exec()

	 * that will systematically cause a cgroup_switch()

	 */

	if (next)

		cgrp2 = perf_cgroup_from_task(next);

		cgrp2 = perf_cgroup_from_task(next, NULL);



	/*

	 * only schedule out current cgroup events if we know
@@ -572,11 +576,13 @@ static inline void perf_cgroup_sched_in(struct task_struct *prev, 
	rcu_read_lock();

	/*

	 * we come here when we know perf_cgroup_events > 0

	 * we do not need to pass the ctx here because we know

	 * we are holding the rcu lock

	 */

	cgrp1 = perf_cgroup_from_task(task);

	cgrp1 = perf_cgroup_from_task(task, NULL);



	/* prev can never be NULL */

	cgrp2 = perf_cgroup_from_task(prev);

	cgrp2 = perf_cgroup_from_task(prev, NULL);



	/*

	 * only need to schedule in cgroup events if we are changing