From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hiroshi Shimamoto Subject: Re: [PATCH] sched: fix race in schedule Date: Mon, 10 Mar 2008 14:07:12 -0700 Message-ID: <47D5A300.2010608@ct.jp.nec.com> References: <47D57770.50909@ct.jp.nec.com> <1205174197.8514.159.camel@twins> <47D593A5.5060906@ct.jp.nec.com> <1205181256.6241.320.camel@lappy> <47D59FFB.8030201@ct.jp.nec.com> <1205182914.6241.322.camel@lappy> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Ingo Molnar , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, hpj@urpla.net, stable To: Peter Zijlstra Return-path: Received: from TYO202.gate.nec.co.jp ([202.32.8.206]:45383 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752321AbYCJVII (ORCPT ); Mon, 10 Mar 2008 17:08:08 -0400 In-Reply-To: <1205182914.6241.322.camel@lappy> Sender: linux-rt-users-owner@vger.kernel.org List-ID: Peter Zijlstra wrote: > On Mon, 2008-03-10 at 13:54 -0700, Hiroshi Shimamoto wrote: >> Peter Zijlstra wrote: >>> On Mon, 2008-03-10 at 13:01 -0700, Hiroshi Shimamoto wrote: >>> >>>> thanks, your patch looks nice to me. >>>> I had focused setprio, on_rq=0 and running=1 situation, it makes me to >>>> fix these functions. >>>> But one point, I've just noticed. I'm not sure on same situation against >>>> sched_rt. I think the pre_schedule() of rt has chance to drop rq lock. >>>> Is it OK? >>> Ah, you are quite right, that'll teach me to rush out a patch just >>> because dinner is ready :-). >>> >>> How about we submit the following patch for mainline and CC -stable to >>> fix .23 and .24: >> thanks for working, I'm OK, and will test it soon. >> IIRC, it came from the group scheduling, .23 probably doesn't have this issue. > > Might not have this exact race, but I've checked both .23 and .24, both > can unlock the rq before we do ->put_prev_task(), leaving a window for > potential nasties. I'm rather safe than sorry :-) Ah, you're correct. I haven't gotten out from the first situation yet :-) thanks, Hiroshi Shimamoto