From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756221Ab1CLXA1 (ORCPT ); Sat, 12 Mar 2011 18:00:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:14674 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756146Ab1CLW7z (ORCPT ); Sat, 12 Mar 2011 17:59:55 -0500 From: Jiri Olsa To: rostedt@goodmis.org, fweisbec@gmail.com, mingo@redhat.com Cc: linux-kernel@vger.kernel.org, oleg@redhat.com, Jiri Olsa Subject: [PATCH 2/2] tracing - putting cond_resched into tace_pipe loop Date: Sat, 12 Mar 2011 23:59:46 +0100 Message-Id: <1299970786-8075-3-git-send-email-jolsa@redhat.com> In-Reply-To: <1299970786-8075-1-git-send-email-jolsa@redhat.com> References: <1299970786-8075-1-git-send-email-jolsa@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adding cond_resched call to the tracing_read_pipe while loop. Plus check for signal to leave the loop. This will protect us from soft lockup on NON preemptive kernels and improve latency. Thanks a lot to Oleg Nestorov for helping me to nail this down. wbr, jirka Signed-off-by: Jiri Olsa --- kernel/trace/trace.c | 13 +++++++++++++ 1 files changed, 13 insertions(+), 0 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 20d84f8..7d66476 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3237,10 +3237,23 @@ waitagain: * One of the trace_seq_* functions is not used properly. */ WARN_ON(iter->seq.full); + + /* + * There's a chance this loop might get quite tight, + * causing latency in non preemptive kernel. + */ + cond_resched(); + if (signal_pending(current)) { + sret = -EINTR; + break; + } } trace_access_unlock(iter->cpu_file); trace_event_read_unlock(); + if (sret == -EINTR) + goto out; + /* Now copy what we have to the user */ sret = trace_seq_to_user(&iter->seq, ubuf, cnt); if (iter->seq.readpos >= iter->seq.len) -- 1.7.1