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 F06BDC433EF for ; Mon, 3 Jan 2022 13:54:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233234AbiACNyh (ORCPT ); Mon, 3 Jan 2022 08:54:37 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:57736 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229531AbiACNye (ORCPT ); Mon, 3 Jan 2022 08:54:34 -0500 Date: Mon, 3 Jan 2022 14:54:31 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1641218073; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=s+KBghPb4YbTCFpwaI5dNaX5KTm96nhcPYF43GxcRUE=; b=LZxNq96AE4KdjkEMj14zH5gBv0W/V0Xf/m18z9vsXdjyEt9F/rLAPhL8hl4BPl0txT1/oD AlE4YvaWdvjuzlfnQF1q/z9hzbPGO9TECk9C+Sjz8PIjTrrGcuk6EFv/fT1uZKBgQWroQe ypLCj3W63QKmmo+rf1+GOhpgy6sRV4HFBbUumq4FTP9VmWUTbPnOfYUD3016jv4K5hQzo9 EoHz/6AeCMABBsLJHjqXqnID+72t0Zhocb19eJiTt7wGkzLxacSwMe09DDvh+j97zfYrkb Tk39BeftMXApsLFHAJczpzbzRqtD/ZvY2e/YXMv9LUiERbZNb72zADpBr+VXgQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1641218073; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=s+KBghPb4YbTCFpwaI5dNaX5KTm96nhcPYF43GxcRUE=; b=H9NxDqcnSvrEm5479zg41Jb+DYGrdr0PKZVyHCr87aEQmaGDVJ/3Vb/BCGi23jrGqMDrun azQRhMJUZeKId4CQ== From: Sebastian Andrzej Siewior To: Andrew Morton Cc: David Howells , linux-kernel@vger.kernel.org, linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org, Tejun Heo , Gregor Beck , Thomas Gleixner , Greg Kroah-Hartman Subject: Re: [PATCH REPOST REPOST v2] fscache: Use only one fscache_object_cong_wait. Message-ID: References: <20211223163500.2625491-1-bigeasy@linutronix.de> <901885.1640279829@warthog.procyon.org.uk> <20211226162030.fc5340c2278c95342690467d@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20211226162030.fc5340c2278c95342690467d@linux-foundation.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-12-26 16:20:30 [-0800], Andrew Morton wrote: > On Thu, 23 Dec 2021 19:15:09 +0100 Sebastian Andrzej Siewior wrote: > > > On 2021-12-23 17:17:09 [+0000], David Howells wrote: > > > Thanks, but this is gone in the upcoming fscache rewrite. I'm hoping that > > > will get in the next merge window. > > > > Yes, I noticed that. What about current tree, v5.16-rc6 and less? > > Shouldn't this be addressed? > > If the bug is serious enough to justify a -stable backport then yes, we > should merge a fix such as this ahead of the fscache rewrite, so we > have something suitable for backporting. > > Is the bug serious enough? > > Or is the bug in a not-yet-noticed state? In other words, is it > possible that four years from now, someone will hit this bug in a > 5.15-based kernel and will then wish we'd backported a fix? I can't answer how serious it is but: - with CONFIG_DEBUG_PREEMPT enabled there has to be a visible backtrace due this_cpu_ptr() usage. - because of schedule_timeout(60 * HZ) there is no visible hang. It should be either woken up properly (via the waitqueue) or after a minute due to the timeout. both things don't look good in general. Sebastian