From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754367Ab1BWMHB (ORCPT ); Wed, 23 Feb 2011 07:07:01 -0500 Received: from hera.kernel.org ([140.211.167.34]:56506 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754203Ab1BWMG7 (ORCPT ); Wed, 23 Feb 2011 07:06:59 -0500 Date: Wed, 23 Feb 2011 12:06:27 GMT From: tip-bot for Stephane Eranian Cc: linux-kernel@vger.kernel.org, eranian@google.com, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, tglx@linutronix.de, eranian@gmail.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, eranian@google.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, tglx@linutronix.de, eranian@gmail.com, mingo@elte.hu In-Reply-To: <4d5e76b8.815bdf0a.7ac3.774f@mx.google.com> References: <4d5e76b8.815bdf0a.7ac3.774f@mx.google.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf_events: Fix rcu and locking issues with cgroup support Message-ID: Git-Commit-ID: 3f7cce3c18188a067d463749168bdda5abc5b0f7 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Wed, 23 Feb 2011 12:06:28 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 3f7cce3c18188a067d463749168bdda5abc5b0f7 Gitweb: http://git.kernel.org/tip/3f7cce3c18188a067d463749168bdda5abc5b0f7 Author: Stephane Eranian AuthorDate: Fri, 18 Feb 2011 14:40:01 +0200 Committer: Ingo Molnar CommitDate: Wed, 23 Feb 2011 11:35:46 +0100 perf_events: Fix rcu and locking issues with cgroup support This patches ensures that we do not end up calling perf_cgroup_from_task() when there is no cgroup event. This avoids potential RCU and locking issues. The change in perf_cgroup_set_timestamp() ensures we check against ctx->nr_cgroups. It also avoids calling perf_clock() tiwce in a row. It also ensures we do need to grab ctx->lock before calling the function. We drop update_cgrp_time() from task_clock_event_read() because it is not needed. This also avoids having to deal with perf_cgroup_from_task(). Thanks to Peter Zijlstra for his help on this. Signed-off-by: Stephane Eranian Signed-off-by: Peter Zijlstra LKML-Reference: <4d5e76b8.815bdf0a.7ac3.774f@mx.google.com> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 40 +++++++++++++++++++++++++++++----------- 1 files changed, 29 insertions(+), 11 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index a0a6987..dadeaea 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -201,6 +201,11 @@ __get_cpu_context(struct perf_event_context *ctx) #ifdef CONFIG_CGROUP_PERF +/* + * Must ensure cgroup is pinned (css_get) before calling + * this function. In other words, we cannot call this function + * if there is no cgroup event for the current CPU context. + */ static inline struct perf_cgroup * perf_cgroup_from_task(struct task_struct *task) { @@ -268,28 +273,41 @@ static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx) static inline void update_cgrp_time_from_event(struct perf_event *event) { - struct perf_cgroup *cgrp = perf_cgroup_from_task(current); + struct perf_cgroup *cgrp; + /* - * do not update time when cgroup is not active + * ensure we access cgroup data only when needed and + * when we know the cgroup is pinned (css_get) */ - if (!event->cgrp || cgrp != event->cgrp) + if (!is_cgroup_event(event)) return; - __update_cgrp_time(event->cgrp); + cgrp = perf_cgroup_from_task(current); + /* + * Do not update time when cgroup is not active + */ + if (cgrp == event->cgrp) + __update_cgrp_time(event->cgrp); } static inline void -perf_cgroup_set_timestamp(struct task_struct *task, u64 now) +perf_cgroup_set_timestamp(struct task_struct *task, + struct perf_event_context *ctx) { struct perf_cgroup *cgrp; struct perf_cgroup_info *info; - if (!task) + /* + * ctx->lock held by caller + * ensure we do not access cgroup data + * unless we have the cgroup pinned (css_get) + */ + if (!task || !ctx->nr_cgroups) return; cgrp = perf_cgroup_from_task(task); info = this_cpu_ptr(cgrp->info); - info->timestamp = now; + info->timestamp = ctx->timestamp; } #define PERF_CGROUP_SWOUT 0x1 /* cgroup switch out every event */ @@ -494,7 +512,8 @@ static inline int perf_cgroup_connect(pid_t pid, struct perf_event *event, } static inline void -perf_cgroup_set_timestamp(struct task_struct *task, u64 now) +perf_cgroup_set_timestamp(struct task_struct *task, + struct perf_event_context *ctx) { } @@ -1613,7 +1632,7 @@ static int __perf_event_enable(void *info) /* * set current task's cgroup time reference point */ - perf_cgroup_set_timestamp(current, perf_clock()); + perf_cgroup_set_timestamp(current, ctx); __perf_event_mark_enabled(event, ctx); @@ -2048,7 +2067,7 @@ ctx_sched_in(struct perf_event_context *ctx, now = perf_clock(); ctx->timestamp = now; - perf_cgroup_set_timestamp(task, now); + perf_cgroup_set_timestamp(task, ctx); /* * First go through the list and put on any pinned groups * in order to give them the best chance of going on. @@ -5795,7 +5814,6 @@ static void task_clock_event_read(struct perf_event *event) if (!in_nmi()) { update_context_time(event->ctx); - update_cgrp_time_from_event(event); time = event->ctx->time; } else { u64 now = perf_clock();