Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755408Ab3JHOlH (ORCPT ); Tue, 8 Oct 2013 10:41:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:28241 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753592Ab3JHOlB (ORCPT ); Tue, 8 Oct 2013 10:41:01 -0400 Date: Tue, 8 Oct 2013 16:34:00 +0200 From: Oleg Nesterov To: Linus Torvalds Cc: Fengguang Wu , Peter Zijlstra , Ingo Molnar , Linux Kernel Mailing List Subject: Re: [x86] BUG: unable to handle kernel paging request at 00740060 Message-ID: <20131008143400.GA14721@redhat.com> References: <20131005234430.GA22485@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1237 Lines: 33 I'll try to find other messages to understand what you are talking about, just one note for now.... On 10/07, Linus Torvalds wrote: > > Your oops makes very little sense, it looks like task_work_run() just > called out to random crap, probably because the work was already > released, so "work->func()" ends up being bad. Or task_work_run() can hit work->func == NULL if do_exit() is called twice if, say, the task does BUG() after exit_task_work(). > participants anyway, just in case there is some race. The comment says > that it can race with task_work_cancel() playing with *work. Oleg, > comments? The comment tries to say that if we are racing with task_work_cancel() it can't delete the first entry == work, we won the race, its cmpxchg(task->task_works) should fail. Howver, task_work_cancel() can delete one of the next entries and change, say, work->next. And we need to wait anyway if it scans this list. I'll try to recheck, but so far I do not see anything wrong. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/