From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752815Ab2LVE0I (ORCPT ); Fri, 21 Dec 2012 23:26:08 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:28261 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751595Ab2LVEZz (ORCPT ); Fri, 21 Dec 2012 23:25:55 -0500 X-Authority-Analysis: v=2.0 cv=QPnqt33L c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=Ciwy3NGCPMMA:10 a=V2H3lkE-9R8A:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=o7EQseuvQBcA:10 a=VwQbUJbxAAAA:8 a=2LSXkEi98N5-jCFdiEkA:9 a=Zh68SRI7RUMA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-Id: <20121222042554.207940346@goodmis.org> User-Agent: quilt/0.60-1 Date: Fri, 21 Dec 2012 23:25:19 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , John Kacur , Subject: [PATCH RT 4/5] block: Use cpu_chill() for retry loops References: <20121222042515.867823077@goodmis.org> Content-Disposition: inline; filename=0004-block-Use-cpu_chill-for-retry-loops.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Gleixner Retry loops on RT might loop forever when the modifying side was preempted. Steven also observed a live lock when there was a concurrent priority boosting going on. Use cpu_chill() instead of cpu_relax() to let the system make progress. Signed-off-by: Thomas Gleixner Cc: stable-rt@vger.kernel.org --- block/blk-ioc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block/blk-ioc.c b/block/blk-ioc.c index fb95dd2..6b54201 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -8,6 +8,7 @@ #include #include /* for max_pfn/max_low_pfn */ #include +#include #include "blk.h" @@ -110,7 +111,7 @@ static void ioc_release_fn(struct work_struct *work) spin_unlock(q->queue_lock); } else { spin_unlock_irqrestore(&ioc->lock, flags); - cpu_relax(); + cpu_chill(); spin_lock_irqsave_nested(&ioc->lock, flags, 1); } } @@ -188,7 +189,7 @@ retry: spin_unlock(icq->q->queue_lock); } else { spin_unlock_irqrestore(&ioc->lock, flags); - cpu_relax(); + cpu_chill(); goto retry; } } -- 1.7.10.4