Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754245AbbKLKA2 (ORCPT ); Thu, 12 Nov 2015 05:00:28 -0500 Received: from mail-pa0-f50.google.com ([209.85.220.50]:35031 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754114AbbKLKAS (ORCPT ); Thu, 12 Nov 2015 05:00:18 -0500 From: Stephane Eranian To: linux-kernel@vger.kernel.org Cc: acme@redhat.com, peterz@infradead.org, mingo@elte.hu, ak@linux.intel.com, edumazet@google.com Subject: [PATCH v3 2/2] perf/core: robustify perf_cgroup_from_task rcu checks Date: Thu, 12 Nov 2015 11:00:04 +0100 Message-Id: <1447322404-10920-3-git-send-email-eranian@google.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1447322404-10920-1-git-send-email-eranian@google.com> References: <1447322404-10920-1-git-send-email-eranian@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4600 Lines: 125 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 hold the rcu read lock. Signed-off-by: Stephane Eranian --- arch/x86/kernel/cpu/perf_event_intel_cqm.c | 2 +- include/linux/perf_event.h | 6 ++++-- kernel/events/core.c | 20 +++++++++++++------- 3 files changed, 18 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_cqm.c b/arch/x86/kernel/cpu/perf_event_intel_cqm.c index 377e8f8..a316ca9 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_cqm.c +++ b/arch/x86/kernel/cpu/perf_event_intel_cqm.c @@ -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; } diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d841d33..f9828a4 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -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 */ diff --git a/kernel/events/core.c b/kernel/events/core.c index ea0bdc5..3dbc3c2 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -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 -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/