From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id rTlADjcnHluyBQAAmS7hNA ; Mon, 11 Jun 2018 07:39:35 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 1BCE6606FA; Mon, 11 Jun 2018 07:39:35 +0000 (UTC) Authentication-Results: smtp.codeaurora.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="k8zLwNvY" X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,T_DKIMWL_WL_MED, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id B9D57601D2; Mon, 11 Jun 2018 07:39:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org B9D57601D2 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932385AbeFKHjb (ORCPT + 20 others); Mon, 11 Jun 2018 03:39:31 -0400 Received: from mail-pg0-f66.google.com ([74.125.83.66]:41397 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754140AbeFKHj2 (ORCPT ); Mon, 11 Jun 2018 03:39:28 -0400 Received: by mail-pg0-f66.google.com with SMTP id l65-v6so9328864pgl.8 for ; Mon, 11 Jun 2018 00:39:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=e9wiTJgkhYWodmql/X5ryM0JlrJvkdjAPkFig3X5rp4=; b=k8zLwNvYDWDC5JlNs6+/4Y0gR56GZG7g45DamM2GQ30bFhVLhjPi9zjZIbXiyoyZ44 VtGL+C96V7TV+ajcHKow11NjmMQRgD42/q4SIjaTWKIffTii1cqj9UuG+DM9oiqzi76N M4wavJVMmZXOKqhZTzn4va0d5eI/oWpUTmNdIUEdx4SPWXbWte7JR2Q7aLAVXmXIBKJV F/5OoA7PA2DEm7Ho1T23bDrvsLl9W6x0BzU5W2b2ZRcL1t/Qbf26IQLaltPBwKW0qNLM eJYM52ZU0IgKv62khJt6LSBo4RBEHJ0kxt5iHI9j/M+ZbVvfvs9/iJBDwXTssTpI10bV j04w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=e9wiTJgkhYWodmql/X5ryM0JlrJvkdjAPkFig3X5rp4=; b=f92To7V1CKyFcFiEDFwVgyHZ974yJRaXV6TcVkaqSpj8lNgEvaKq12zD3+Thrj6+o4 rFNMfJGDfe549E5v0BZXm7erDUGKYHhApWE+TEAYH22aqgSqckwbWDag0yM0nOBaUvw8 TD4hHEQSgULACAwVy9U8sQdjIQl7CbhO+C98XPT7FNVbFNMZYlY66DQc5y8TNr1u5Q79 wpBhogWbmm1xoYQ+irypmVtjoR2AS3QhH87K97XX6HKzuO0WKpOtfmegoL/kBtAQY06C ltpUMsgNb1yhx6Lb9k73r+e6Ewv8xCs4cDJfAOXFda4Jr9INBp87TDB4XwCZleSqP5k9 C9vg== X-Gm-Message-State: APt69E1oSohS9Mla6d1orDs/+FtbC6MGRMDZe9gul57Lio0MJcWPd/Fw Kaa7bVSO/VyMrfzd1T2dPYCf5XXoGgWXcJw5VGhxFw== X-Google-Smtp-Source: ADUXVKJBopbC5lBQvK9fP5ISp4Jjz+/sJI1Dv5E2R3+w69X5fUHW3zGTBi3+D35NOYerOeTDM0fIklJkbOKyf0PgyJo= X-Received: by 2002:a63:721c:: with SMTP id n28-v6mr13695177pgc.96.1528702767678; Mon, 11 Jun 2018 00:39:27 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a17:90a:ac07:0:0:0:0 with HTTP; Mon, 11 Jun 2018 00:39:07 -0700 (PDT) In-Reply-To: <20180611073038.GK12217@hirez.programming.kicks-ass.net> References: <000000000000283c37056b4a81a5@google.com> <20180611073038.GK12217@hirez.programming.kicks-ass.net> From: Dmitry Vyukov Date: Mon, 11 Jun 2018 09:39:07 +0200 Message-ID: Subject: Re: INFO: task hung in __sb_start_write To: Peter Zijlstra Cc: Tetsuo Handa , Ingo Molnar , Will Deacon , syzbot , linux-fsdevel , LKML , syzkaller-bugs , Al Viro Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 11, 2018 at 9:30 AM, Peter Zijlstra wrote: > On Sun, Jun 10, 2018 at 11:47:56PM +0900, Tetsuo Handa wrote: > >> This looks quite strange that nobody is holding percpu_rw_semaphore for >> write but everybody is stuck trying to hold it for read. (Since there >> is no "X locks held by ..." line without followup "#0:" line, there is >> no possibility that somebody is in TASK_RUNNING state while holding >> percpu_rw_semaphore for write.) >> >> I feel that either API has a bug or API usage is wrong. >> Any idea for debugging this? > > Look at percpu_rwsem_release() and usage. The whole fs freezer thing is > magic. Do you mean that we froze fs? We tried to never-ever issue ioctl(FIFREEZE) during fuzzing. Are there other ways to do this?