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Commit 33801b94 authored by leilei.lin's avatar leilei.lin Committed by Ingo Molnar
Browse files

perf/core: Fix installing cgroup events on CPU 



There's two problems when installing cgroup events on CPUs: firstly
list_update_cgroup_event() only tries to set cpuctx->cgrp for the
first event, if that mismatches on @cgrp we'll not try again for later
additions.

Secondly, when we install a cgroup event into an active context, only
issue an event reprogram when the event matches the current cgroup
context. This avoids a pointless event reprogramming.

Signed-off-by: default avatarleilei.lin <leilei.lin@alibaba-inc.com>
[ Improved the changelog and comments. ]
Signed-off-by: default avatarPeter 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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: brendan.d.gregg@gmail.com
Cc: eranian@gmail.com
Cc: linux-kernel@vger.kernel.org
Cc: yang_oliver@hotmail.com
Link: http://lkml.kernel.org/r/20180306093637.28247-1-linxiulei@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8d5bce0c

kernel/events/core.c

+35 −11
Original line number Diff line number Diff line
@@ -937,27 +937,39 @@ list_update_cgroup_event(struct perf_event *event, 
	if (!is_cgroup_event(event))

		return;



	if (add && ctx->nr_cgroups++)

		return;

	else if (!add && --ctx->nr_cgroups)

		return;

	/*

	 * Because cgroup events are always per-cpu events,

	 * this will always be called from the right CPU.

	 */

	cpuctx = __get_cpu_context(ctx);

	cpuctx_entry = &cpuctx->cgrp_cpuctx_entry;

	/* cpuctx->cgrp is NULL unless a cgroup event is active in this CPU .*/

	if (add) {



	/*

	 * Since setting cpuctx->cgrp is conditional on the current @cgrp

	 * matching the event's cgroup, we must do this for every new event,

	 * because if the first would mismatch, the second would not try again

	 * and we would leave cpuctx->cgrp unset.

	 */

	if (add && !cpuctx->cgrp) {

		struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);



		list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list));

		if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup))

			cpuctx->cgrp = cgrp;

	} else {

		list_del(cpuctx_entry);

		cpuctx->cgrp = NULL;

	}



	if (add && ctx->nr_cgroups++)

		return;

	else if (!add && --ctx->nr_cgroups)

		return;



	/* no cgroup running */

	if (!add)

		cpuctx->cgrp = NULL;



	cpuctx_entry = &cpuctx->cgrp_cpuctx_entry;

	if (add)

		list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list));

	else

		list_del(cpuctx_entry);

}



#else /* !CONFIG_CGROUP_PERF */
@@ -2489,6 +2501,18 @@ static int __perf_install_in_context(void *info) 
		raw_spin_lock(&task_ctx->lock);

	}



#ifdef CONFIG_CGROUP_PERF

	if (is_cgroup_event(event)) {

		/*

		 * If the current cgroup doesn't match the event's

		 * cgroup, we should not try to schedule it.

		 */

		struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);

		reprogram = cgroup_is_descendant(cgrp->css.cgroup,

					event->cgrp->css.cgroup);

	}

#endif



	if (reprogram) {

		ctx_sched_out(ctx, cpuctx, EVENT_TIME);

		add_event_to_ctx(event, ctx);