From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756210Ab0IUOOS (ORCPT ); Tue, 21 Sep 2010 10:14:18 -0400 Received: from hera.kernel.org ([140.211.167.34]:46482 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755761Ab0IUOOQ (ORCPT ); Tue, 21 Sep 2010 10:14:16 -0400 Date: Tue, 21 Sep 2010 14:13:48 GMT From: tip-bot for Peter Zijlstra Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, tj@kernel.org, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, tj@kernel.org, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <20100917093009.308453028@chello.nl> References: <20100917093009.308453028@chello.nl> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf: Avoid RCU vs preemption assumptions Message-ID: Git-Commit-ID: 41945f6ccf1e86f87fddf6b32db9cf431c05fb54 X-Mailer: tip-git-log-daemon 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]); Tue, 21 Sep 2010 14:13:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 41945f6ccf1e86f87fddf6b32db9cf431c05fb54 Gitweb: http://git.kernel.org/tip/41945f6ccf1e86f87fddf6b32db9cf431c05fb54 Author: Peter Zijlstra AuthorDate: Thu, 16 Sep 2010 19:17:24 +0200 Committer: Ingo Molnar CommitDate: Tue, 21 Sep 2010 13:55:44 +0200 perf: Avoid RCU vs preemption assumptions The per-pmu per-cpu context patch converted things from get_cpu_var() to this_cpu_ptr(), but that only works if rcu_read_lock() actually disables preemption, and since there is no such guarantee, we need to fix that. Use the newly introduced {get,put}_cpu_ptr(). Signed-off-by: Peter Zijlstra Cc: Tejun Heo LKML-Reference: <20100917093009.308453028@chello.nl> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 18 ++++++++++++------ 1 files changed, 12 insertions(+), 6 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index baae136..c16158c 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3836,18 +3836,20 @@ static void perf_event_task_event(struct perf_task_event *task_event) rcu_read_lock(); list_for_each_entry_rcu(pmu, &pmus, entry) { - cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); + cpuctx = get_cpu_ptr(pmu->pmu_cpu_context); perf_event_task_ctx(&cpuctx->ctx, task_event); ctx = task_event->task_ctx; if (!ctx) { ctxn = pmu->task_ctx_nr; if (ctxn < 0) - continue; + goto next; ctx = rcu_dereference(current->perf_event_ctxp[ctxn]); } if (ctx) perf_event_task_ctx(ctx, task_event); +next: + put_cpu_ptr(pmu->pmu_cpu_context); } rcu_read_unlock(); } @@ -3969,16 +3971,18 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event) rcu_read_lock(); list_for_each_entry_rcu(pmu, &pmus, entry) { - cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); + cpuctx = get_cpu_ptr(pmu->pmu_cpu_context); perf_event_comm_ctx(&cpuctx->ctx, comm_event); ctxn = pmu->task_ctx_nr; if (ctxn < 0) - continue; + goto next; ctx = rcu_dereference(current->perf_event_ctxp[ctxn]); if (ctx) perf_event_comm_ctx(ctx, comm_event); +next: + put_cpu_ptr(pmu->pmu_cpu_context); } rcu_read_unlock(); } @@ -4152,19 +4156,21 @@ got_name: rcu_read_lock(); list_for_each_entry_rcu(pmu, &pmus, entry) { - cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); + cpuctx = get_cpu_ptr(pmu->pmu_cpu_context); perf_event_mmap_ctx(&cpuctx->ctx, mmap_event, vma->vm_flags & VM_EXEC); ctxn = pmu->task_ctx_nr; if (ctxn < 0) - continue; + goto next; ctx = rcu_dereference(current->perf_event_ctxp[ctxn]); if (ctx) { perf_event_mmap_ctx(ctx, mmap_event, vma->vm_flags & VM_EXEC); } +next: + put_cpu_ptr(pmu->pmu_cpu_context); } rcu_read_unlock();