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[23.128.96.38]) by mx.google.com with ESMTPS id ck1-20020a056a02090100b005c671034477si4785713pgb.539.2023.12.05.04.01.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Dec 2023 04:01:14 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.38 as permitted sender) client-ip=23.128.96.38; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.38 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by fry.vger.email (Postfix) with ESMTP id CDF3E80A41B3; Tue, 5 Dec 2023 04:01:11 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at fry.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347038AbjLEMAq (ORCPT + 99 others); Tue, 5 Dec 2023 07:00:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48542 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347122AbjLEMAn (ORCPT ); Tue, 5 Dec 2023 07:00:43 -0500 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 36057116 for ; Tue, 5 Dec 2023 04:00:49 -0800 (PST) Received: from fsav411.sakura.ne.jp (fsav411.sakura.ne.jp [133.242.250.110]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 3B5C0loc069588; Tue, 5 Dec 2023 21:00:47 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav411.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav411.sakura.ne.jp); Tue, 05 Dec 2023 21:00:46 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav411.sakura.ne.jp) Received: from [192.168.1.6] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 3B5C0k9V069585 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Tue, 5 Dec 2023 21:00:46 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <317e077b-71a7-4112-a7d0-5c49efce4f39@I-love.SAKURA.ne.jp> Date: Tue, 5 Dec 2023 21:00:46 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [kernel?] possible deadlock in stack_depot_put Content-Language: en-US To: Hillf Danton , syzbot Cc: linux-kernel@vger.kernel.org, Matthew Wilcox , Petr Mladek , John Ogness , Waiman Long , Linus Torvalds , syzkaller-bugs@googlegroups.com References: <000000000000784b1c060b0074a2@google.com> <20231205113107.1324-1-hdanton@sina.com> From: Tetsuo Handa In-Reply-To: <20231205113107.1324-1-hdanton@sina.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on fry.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (fry.vger.email [0.0.0.0]); Tue, 05 Dec 2023 04:01:12 -0800 (PST) On 2023/12/05 20:31, Hillf Danton wrote: > Unlike down_trylock(), mutex_trylock() is unable to trigger any lockdep > warning, so why is a binary semaphore prefered over mutex? The mutex has limitations which makes it impossible to use for console lock. https://elixir.bootlin.com/linux/v6.7-rc4/source/kernel/locking/mutex.c#L537 By the way, this is a KASAN bug saying "refcount_t: underflow; use-after-free.". Possibly a candidate for printk_deferred_enter() user?