From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97265C433F5 for ; Mon, 10 Sep 2018 13:56:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F8A220855 for ; Mon, 10 Sep 2018 13:56:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="mjKkxC/A" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F8A220855 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728854AbeIJSuy (ORCPT ); Mon, 10 Sep 2018 14:50:54 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:34256 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728184AbeIJSuy (ORCPT ); Mon, 10 Sep 2018 14:50:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=EUbYCfEDCsJGsk9vZGqMRilQSFrjcI3at2vjd9xn8mM=; b=mjKkxC/APFY0vVUMBI2NZdmdW /xGnghsHWPPtiwEz2hxoCZIQP/gnsUtG/FtwvYsACPhQUJ+lSgLNNA17DYxEMCsnW4fIXCJ+7QZEu X53vic0H6XaWCEV53HisdDkMgmylymWa3+IZ+kqMxMeXr4fTXWpy6V/JlivJ0UGkZBjXjZL+mm6nP NVDcDS0QtXKBSPZF0Zw+8zSa2DdrLm9P8b98cm3VDSe784lYASQVT4ZvIRZJ73fHoX/16ZkQH62cn hAaxc5Fj5oQR+up7u1weGGpzL/U0qqmkcKlkjU2kALAe4EsBrYF6Ed7VKHYI5O69/IfZrMqK8QIrW RAZc230XQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fzMg2-0000MD-QP; Mon, 10 Sep 2018 13:56:31 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B3C25202C1A02; Mon, 10 Sep 2018 15:56:27 +0200 (CEST) Date: Mon, 10 Sep 2018 15:56:27 +0200 From: Peter Zijlstra To: Jia-Ju Bai Cc: mingo@redhat.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, Thomas Gleixner , Steven Rostedt Subject: Re: [PATCH V2] kernel: locking: rtmutex: Fix a possible sleep-in-atomic-context bug in rt_mutex_handle_deadlock() Message-ID: <20180910135627.GL24106@hirez.programming.kicks-ass.net> References: <20180811030037.14885-1-baijiaju1990@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180811030037.14885-1-baijiaju1990@gmail.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 11, 2018 at 11:00:37AM +0800, Jia-Ju Bai wrote: You forgot to Cc the person who wrote this code... > kernel/locking/rtmutex.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c > index 2823d4163a37..8f25a289abe8 100644 > --- a/kernel/locking/rtmutex.c > +++ b/kernel/locking/rtmutex.c > @@ -1205,7 +1205,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, > } > > static void rt_mutex_handle_deadlock(int res, int detect_deadlock, > - struct rt_mutex_waiter *w) > + struct rt_mutex_waiter *w, struct rt_mutex *lock) > { > /* > * If the result is not -EDEADLOCK or the caller requested > @@ -1218,6 +1218,8 @@ static void rt_mutex_handle_deadlock(int res, int detect_deadlock, > * Yell lowdly and stop the task right here. > */ > rt_mutex_print_deadlock(w); > + /* We're not going anywhere, release the wait_lock */ > + raw_spin_unlock_irq(&lock->wait_lock); > while (1) { > set_current_state(TASK_INTERRUPTIBLE); > schedule(); > @@ -1269,7 +1271,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, > if (unlikely(ret)) { > __set_current_state(TASK_RUNNING); > remove_waiter(lock, &waiter); > - rt_mutex_handle_deadlock(ret, chwalk, &waiter); > + rt_mutex_handle_deadlock(ret, chwalk, &waiter, lock); > } The patch is correct; but I can't find myself liking it very much. This dinly little single use function is growing a lot of arguments. The alternative is something like the below; not sure myself though. Thomas? diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 2823d4163a37..a44d4034e232 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1204,18 +1204,10 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, return ret; } -static void rt_mutex_handle_deadlock(int res, int detect_deadlock, - struct rt_mutex_waiter *w) +static void rt_mutex_handle_deadlock(struct rt_mutex_waiter *w) { /* - * If the result is not -EDEADLOCK or the caller requested - * deadlock detection, nothing to do here. - */ - if (res != -EDEADLOCK || detect_deadlock) - return; - - /* - * Yell lowdly and stop the task right here. + * Yell loudly and stop the task right here. */ rt_mutex_print_deadlock(w); while (1) { @@ -1269,7 +1261,10 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, if (unlikely(ret)) { __set_current_state(TASK_RUNNING); remove_waiter(lock, &waiter); - rt_mutex_handle_deadlock(ret, chwalk, &waiter); + if (chwalk == RT_MUTEX_MIN_CHAINWALK && ret == -EDEADLOCK) { + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); + rt_mutex_handle_deadlock(&waiter); + } } /*