From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756328Ab0ETTme (ORCPT ); Thu, 20 May 2010 15:42:34 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:46649 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754245Ab0ETTmd (ORCPT ); Thu, 20 May 2010 15:42:33 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:x-mailer-version; b=HDrNwkB3u97g4usqFaTjTUcpgyW2Y3wftMsA/s+XFLH2TNE1pQNxgSW+U8+HyNEjOU /vR/vZvGDnIJaE0nBtoWFp9zeMMPWLvAMOdwFvYq3hd+vJz2R7u7Z0g7I7/vrBZlwl58 YwnqNdSJGUKnbkB6LbRQX2WZ4kGQ9Ep+JCnC0= From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , Peter Zijlstra , Arnaldo Carvalho de Melo , Paul Mackerras , Stephane Eranian , Robert Richter Subject: [GIT PULL] perf fix (preempt count imbalance on buffer) Date: Thu, 20 May 2010 21:42:38 +0200 Message-Id: <1274384558-19680-1-git-send-regression-fweisbec@gmail.com> X-Mailer: git-send-regression X-Mailer-version: 0.1, "The maintainer couldn't reproduce after one week full time debugging" special version. Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo, Please pull the perf/core branch that can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing.git perf/core Thanks, Frederic --- Frederic Weisbecker (1): perf: Fix forgotten preempt_enable by nested writers kernel/perf_event.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) --- commit acd35a463cb2a8d2b28e094d718cf6e653ad7191 Author: Frederic Weisbecker Date: Thu May 20 21:28:34 2010 +0200 perf: Fix forgotten preempt_enable by nested writers A writer that gets a reference to the buffer handle disables preemption. When we put that reference, we check if we are the outer most writer and if not, we simply return and defer the head update to the outer most writer. The problem here is that preemption is only reenabled by the outer most, that produces preemption count imbalance for every nested writer that exit. So just don't forget to always re-enable preemption when we put the buffer reference, whoever we are. Fixes lots of sleeping in atomic warnings, visible with lock events recording. Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras Cc: Stephane Eranian Cc: Robert Richter diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 2a060be..45b7aec 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -2933,7 +2933,7 @@ again: */ if (!local_dec_and_test(&data->nest)) - return; + goto out; /* * Publish the known good head. Rely on the full barrier implied @@ -2954,6 +2954,7 @@ again: if (handle->wakeup != local_read(&data->wakeup)) perf_output_wakeup(handle); + out: preempt_enable(); }