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 E8496C4332F for ; Thu, 12 May 2022 11:22:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353313AbiELLWG (ORCPT ); Thu, 12 May 2022 07:22:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353390AbiELLVJ (ORCPT ); Thu, 12 May 2022 07:21:09 -0400 Received: from lgeamrelo11.lge.com (lgeamrelo12.lge.com [156.147.23.52]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id BBD8B15EE41 for ; Thu, 12 May 2022 04:20:05 -0700 (PDT) Received: from unknown (HELO lgemrelse6q.lge.com) (156.147.1.121) by 156.147.23.52 with ESMTP; 12 May 2022 20:20:03 +0900 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: byungchul.park@lge.com Received: from unknown (HELO localhost.localdomain) (10.177.244.38) by 156.147.1.121 with ESMTP; 12 May 2022 20:20:03 +0900 X-Original-SENDERIP: 10.177.244.38 X-Original-MAILFROM: byungchul.park@lge.com From: Byungchul Park To: tj@kernel.org Cc: torvalds@linux-foundation.org, damien.lemoal@opensource.wdc.com, linux-ide@vger.kernel.org, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org, peterz@infradead.org, will@kernel.org, tglx@linutronix.de, rostedt@goodmis.org, joel@joelfernandes.org, sashal@kernel.org, daniel.vetter@ffwll.ch, chris@chris-wilson.co.uk, duyuyang@gmail.com, johannes.berg@intel.com, tytso@mit.edu, willy@infradead.org, david@fromorbit.com, amir73il@gmail.com, gregkh@linuxfoundation.org, kernel-team@lge.com, linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, minchan@kernel.org, hannes@cmpxchg.org, vdavydov.dev@gmail.com, sj@kernel.org, jglisse@redhat.com, dennis@kernel.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, vbabka@suse.cz, ngupta@vflare.org, linux-block@vger.kernel.org, paolo.valente@linaro.org, josef@toxicpanda.com, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, jack@suse.cz, jack@suse.com, jlayton@kernel.org, dan.j.williams@intel.com, hch@infradead.org, djwong@kernel.org, dri-devel@lists.freedesktop.org, rodrigosiqueiramelo@gmail.com, melissa.srw@gmail.com, hamohammed.sa@gmail.com, 42.hyeyoo@gmail.com, mcgrof@kernel.org, holt@sgi.com Subject: Re: [REPORT] syscall reboot + umh + firmware fallback Date: Thu, 12 May 2022 20:18:24 +0900 Message-Id: <1652354304-17492-1-git-send-email-byungchul.park@lge.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: References: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Tejun wrote: > Hello, Hello, > I'm not sure I'm reading it correctly but it looks like "process B" column I think you're interpreting the report correctly. > is superflous given that it's waiting on the same lock to do the same thing > that A is already doing (besides, you can't really halt the machine twice). Indeed! I've been in a daze. I thought kernel_halt() can be called twice by two different purposes. Sorry for the noise. > What it's reporting seems to be ABBA deadlock between A waiting on > umhelper_sem and C waiting on fw_st->completion. The report seems spurious: > > 1. wait_for_completion_killable_timeout() doesn't need someone to wake it up > to make forward progress because it will unstick itself after timeout > expires. I have a question about this one. Yes, it would never been stuck thanks to timeout. However, IIUC, timeouts are not supposed to expire in normal cases. So I thought a timeout expiration means not a normal case so need to inform it in terms of dependency so as to prevent further expiraton. That's why I have been trying to track even timeout'ed APIs. Do you think DEPT shouldn't track timeout APIs? If I was wrong, I shouldn't track the timeout APIs any more. > 2. complete_all() from __fw_load_abort() isn't the only source of wakeup. > The fw loader can be, and mainly should be, woken up by firmware loading > actually completing instead of being aborted. This is the point I'd like to ask. In normal cases, fw_load_done() might happen, of course, if the loading gets completed. However, I was wondering if the kernel ensures either fw_load_done() or fw_load_abort() to be called by *another* context while kernel_halt(). > Thanks. Thank you very much! Byungchul > > -- > tejun >