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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 276D0C433EF for ; Fri, 13 May 2022 15:17:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377250AbiEMPR3 (ORCPT ); Fri, 13 May 2022 11:17:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34418 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352924AbiEMPR2 (ORCPT ); Fri, 13 May 2022 11:17:28 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 011305DA0C for ; Fri, 13 May 2022 08:17:27 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id B1EEA21AAC; Fri, 13 May 2022 15:17:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1652455046; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xgzHWCVSXbaQuTfBvigH/Py+Yk7WuUF5pNuO7TdQ+kQ=; b=mHwdDX61yRE6wHm1q5L8YeHcDTKT3wZ7Lx/QDNUdezVJq1eT2p/OUkmgTzaz6JXCLsa5qk 37nEUSzg98EpxHg0eUqZKfc3Oouafat7eB6OL8tqbrY1LRPoYhFY9pJfPMSZFt8QsAszFo ZPc8D2SjXvWJ/opY65mazP6QAUIeniY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1652455046; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xgzHWCVSXbaQuTfBvigH/Py+Yk7WuUF5pNuO7TdQ+kQ=; b=z3QpvHd08XporHTwlfF2a1GhCduA3N2yZ6/9WGYXtBjmFWnK6t3EWA6vkpSjO12GF0wUHb RBhotxptPKFLclBQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3842213446; Fri, 13 May 2022 15:17:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 3n+pAIV2fmJJIQAAMHmgww (envelope-from ); Fri, 13 May 2022 15:17:25 +0000 Message-ID: <428a70b3-f671-e6fb-93d1-0a975da35ad8@suse.de> Date: Fri, 13 May 2022 23:17:22 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH] bcache: remove unnecessary flush_workqueue Content-Language: en-US To: =?UTF-8?B?5p2O56OK?= Cc: kent.overstreet@gmail.com, linux-bcache@vger.kernel.org, Li Lei References: <20220327072038.12385-1-lilei@szsandstone.com> <40862b68-e81d-089b-d713-b0e6e2bd7e04@suse.de> From: Coly Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On 4/9/22 9:17 AM, 李磊 wrote: > Coly Li 于2022年4月8日周五 00:54写道： >> On 3/27/22 3:20 PM, Li Lei wrote: >>> All pending works will be drained by destroy_workqueue(), no need to call >>> flush_workqueue() explicitly. >>> >>> Signed-off-by: Li Lei >>> --- >>> drivers/md/bcache/writeback.c | 5 ++--- >>> 1 file changed, 2 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c >>> index 9ee0005874cd..2a6d9f39a9b1 100644 >>> --- a/drivers/md/bcache/writeback.c >>> +++ b/drivers/md/bcache/writeback.c >>> @@ -793,10 +793,9 @@ static int bch_writeback_thread(void *arg) >>> } >>> } >>> >>> - if (dc->writeback_write_wq) { >>> - flush_workqueue(dc->writeback_write_wq); >>> + if (dc->writeback_write_wq) >>> destroy_workqueue(dc->writeback_write_wq); >>> - } >>> + >>> cached_dev_put(dc); >>> wait_for_kthread_stop(); >>> >> The above code is from commit 7e865eba00a3 ("bcache: fix potential >> deadlock in cached_def_free()"). I explicitly added extra >> flush_workqueue() was because of workqueue_sysfs_unregister(wq) in >> destory_workqueue(). >> >> workqueue_sysfs_unregister() is not simple because it calls >> device_unregister(), and the code path is long. During reboot I am not >> sure whether extra deadlocking issue might be introduced. So the safe >> way is to explicitly call flush_workqueue() firstly to wait for all >> kwork finished, then destroy it. >> >> It has been ~3 years passed, now I am totally OK with your above change. >> But could you please test your patch with lockdep enabled, and see >> whether there is no lock warning observed? Then I'd like to add it into >> my test directory. >> > OK，I will test this scenario. Any progress? Coly Li