From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755122AbcCBLY0 (ORCPT ); Wed, 2 Mar 2016 06:24:26 -0500 Received: from mga03.intel.com ([134.134.136.65]:40224 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754588AbcCBLYY (ORCPT ); Wed, 2 Mar 2016 06:24:24 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,528,1449561600"; d="scan'208";a="58292869" From: Alexander Shishkin To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , Alexander Shishkin Subject: [PATCH] perf: Fix perf_sched_count derailment Date: Wed, 2 Mar 2016 13:24:14 +0200 Message-Id: <1456917854-29427-1-git-send-email-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.7.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The error path in perf_event_open() is such that asking for a sampling event on a pmu that doesn't generate interrupts will end up in dropping the perf_sched_count even though it hasn't been incremented for this event yet. Given a sufficient amount of these calls, we'll end up disabling scheduler's jump label even though we'd still have active events in the system, thereby facilitating the arrival of the infernal regions upon us. I'm fixing this by moving account_event() inside perf_event_alloc(). Signed-off-by: Alexander Shishkin --- kernel/events/core.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index ce54a68493..1d47d59bb1 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8101,6 +8101,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, } } + /* symmetric to unaccount_event() in _free_event() */ + account_event(event); + return event; err_per_task: @@ -8464,8 +8467,6 @@ SYSCALL_DEFINE5(perf_event_open, } } - account_event(event); - /* * Special case software events and allow them to be part of * any hardware group. @@ -8762,8 +8763,6 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, /* Mark owner so we could distinguish it from user events. */ event->owner = TASK_TOMBSTONE; - account_event(event); - ctx = find_get_context(event->pmu, task, event); if (IS_ERR(ctx)) { err = PTR_ERR(ctx); -- 2.7.0