linux-kernel - [tip:perf/urgent] perf: Disable all pmus on unthrottling and rescheduling

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Message-ID: <tip-443772776c69ac9293d66b4d69fd9af16299cc2a@git.kernel.org>
Date:	Wed, 18 Dec 2013 02:31:41 -0800
From:	tip-bot for Alexander Shishkin <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, eranian@...gle.com, paulus@...ba.org,
	hpa@...or.com, mingo@...nel.org, efault@....de,
	peterz@...radead.org, alexander.shishkin@...ux.intel.com,
	fweisbec@...il.com, ak@...ux.intel.com, tglx@...utronix.de
Subject: [tip:perf/urgent] perf:
  Disable all pmus on unthrottling and rescheduling

Commit-ID:  443772776c69ac9293d66b4d69fd9af16299cc2a
Gitweb:     http://git.kernel.org/tip/443772776c69ac9293d66b4d69fd9af16299cc2a
Author:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
AuthorDate: Mon, 16 Dec 2013 14:17:36 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 17 Dec 2013 15:04:00 +0100

perf: Disable all pmus on unthrottling and rescheduling

Currently, only one PMU in a context gets disabled during unthrottling
and event_sched_{out,in}(), however, events in one context may belong to
different pmus, which results in PMUs being reprogrammed while they are
still enabled.

This means that mixed PMU use [which is rare in itself] resulted in
potentially completely unreliable results: corrupted events, bogus
results, etc.

This patch temporarily disables PMUs that correspond to
each event in the context while these events are being modified.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Mike Galbraith <efault@....de>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Link: http://lkml.kernel.org/r/1387196256-8030-1-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/events/core.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 72348dc..f574401 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1396,6 +1396,8 @@ event_sched_out(struct perf_event *event,
 	if (event->state != PERF_EVENT_STATE_ACTIVE)
 		return;
 
+	perf_pmu_disable(event->pmu);
+
 	event->state = PERF_EVENT_STATE_INACTIVE;
 	if (event->pending_disable) {
 		event->pending_disable = 0;
@@ -1412,6 +1414,8 @@ event_sched_out(struct perf_event *event,
 		ctx->nr_freq--;
 	if (event->attr.exclusive || !cpuctx->active_oncpu)
 		cpuctx->exclusive = 0;
+
+	perf_pmu_enable(event->pmu);
 }
 
 static void
@@ -1652,6 +1656,7 @@ event_sched_in(struct perf_event *event,
 		 struct perf_event_context *ctx)
 {
 	u64 tstamp = perf_event_time(event);
+	int ret = 0;
 
 	if (event->state <= PERF_EVENT_STATE_OFF)
 		return 0;
@@ -1674,10 +1679,13 @@ event_sched_in(struct perf_event *event,
 	 */
 	smp_wmb();
 
+	perf_pmu_disable(event->pmu);
+
 	if (event->pmu->add(event, PERF_EF_START)) {
 		event->state = PERF_EVENT_STATE_INACTIVE;
 		event->oncpu = -1;
-		return -EAGAIN;
+		ret = -EAGAIN;
+		goto out;
 	}
 
 	event->tstamp_running += tstamp - event->tstamp_stopped;
@@ -1693,7 +1701,10 @@ event_sched_in(struct perf_event *event,
 	if (event->attr.exclusive)
 		cpuctx->exclusive = 1;
 
-	return 0;
+out:
+	perf_pmu_enable(event->pmu);
+
+	return ret;
 }
 
 static int
@@ -2743,6 +2754,8 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
 		if (!event_filter_match(event))
 			continue;
 
+		perf_pmu_disable(event->pmu);
+
 		hwc = &event->hw;
 
 		if (hwc->interrupts == MAX_INTERRUPTS) {
@@ -2752,7 +2765,7 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
 		}
 
 		if (!event->attr.freq || !event->attr.sample_freq)
-			continue;
+			goto next;
 
 		/*
 		 * stop the event and update event->count
@@ -2774,6 +2787,8 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
 			perf_adjust_period(event, period, delta, false);
 
 		event->pmu->start(event, delta > 0 ? PERF_EF_RELOAD : 0);
+	next:
+		perf_pmu_enable(event->pmu);
 	}
 
 	perf_pmu_enable(ctx->pmu);
--
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