From patchwork Mon Feb 2 06:09:37 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 5759381 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 827BDBF440 for ; Mon, 2 Feb 2015 06:10:12 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id A35DC20212 for ; Mon, 2 Feb 2015 06:10:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2F96201FB for ; Mon, 2 Feb 2015 06:10:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932427AbbBBGJu (ORCPT ); Mon, 2 Feb 2015 01:09:50 -0500 Received: from cantor2.suse.de ([195.135.220.15]:59415 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932188AbbBBGJt (ORCPT ); Mon, 2 Feb 2015 01:09:49 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 6DAE1AB0C; Mon, 2 Feb 2015 06:09:46 +0000 (UTC) Date: Mon, 2 Feb 2015 17:09:37 +1100 From: NeilBrown To: Linus Torvalds Cc: Fengguang Wu , Peter Zijlstra , LKP , Linux Kernel Mailing List , linux-fsdevel , Shaohua Li , Dan Williams , "linux-btrfs@vger.kernel.org" Subject: Re: __might_sleep() warnings on v3.19-rc6 Message-ID: <20150202170937.4b5ffcb0@notabene.brown> In-Reply-To: References: <20141028142541.GA19097@wfg-t540p.sh.intel.com> <20150201034315.GA20124@wfg-t540p.sh.intel.com> <20150202100338.4fa9eefa@notabene.brown> X-Mailer: Claws Mail 3.10.1-162-g4d0ed6 (GTK+ 2.24.25; x86_64-suse-linux-gnu) MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, T_TVD_MIME_EPI, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Sun, 1 Feb 2015 21:08:12 -0800 Linus Torvalds wrote: > On Sun, Feb 1, 2015 at 3:03 PM, NeilBrown wrote: > > > > I guess I could > > __set_current_state(TASK_RUNNING); > > somewhere to defeat the warning, and add a comment explaining why. > > > > Would that be a good thing? > > Use "sched_annotate_sleep()" instead, but yes, add a comment about why it's ok. > > Linus > -- > 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/ OK - following patch is queued to appear in a pull request tomorrow (I hope). Thanks, NeilBrown From: NeilBrown Date: Mon, 2 Feb 2015 17:08:03 +1100 Subject: [PATCH] md/bitmap: fix a might_sleep() warning. commit 8eb23b9f35aae413140d3fda766a98092c21e9b0 sched: Debug nested sleeps causes false-positive warnings in RAID5 code. This annotation removes them and adds a comment explaining why there is no real problem. Reported-by: Fengguang Wu Signed-off-by: NeilBrown diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c index da3604e73e8a..1695ee5f3ffc 100644 --- a/drivers/md/bitmap.c +++ b/drivers/md/bitmap.c @@ -72,6 +72,19 @@ __acquires(bitmap->lock) /* this page has not been allocated yet */ spin_unlock_irq(&bitmap->lock); + /* It is possible that this is being called inside a + * prepare_to_wait/finish_wait loop from raid5c:make_request(). + * In general it is not permitted to sleep in that context as it + * can cause the loop to spin freely. + * That doesn't apply here as we can only reach this point + * once with any loop. + * When this function completes, either bp[page].map or + * bp[page].hijacked. In either case, this function will + * abort before getting to this point again. So there is + * no risk of a free-spin, and so it is safe to assert + * that sleeping here is allowed. + */ + sched_annotate_sleep(); mappage = kzalloc(PAGE_SIZE, GFP_NOIO); spin_lock_irq(&bitmap->lock);