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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6DB47C3F2CD for ; Wed, 4 Mar 2020 13:54:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 43D7920838 for ; Wed, 4 Mar 2020 13:54:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="oG5B0bbZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729334AbgCDNyG (ORCPT ); Wed, 4 Mar 2020 08:54:06 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:54070 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726413AbgCDNyF (ORCPT ); Wed, 4 Mar 2020 08:54:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=x7QxWeQIS4QmKxDASEYVZavWooJQqeQFhHog8X1BkfA=; b=oG5B0bbZM/UCZziL+BKY3IdPW/ BjJi6lZfeHj8rJ58DlWVG1XXOWQUKB+Qj1OB5wDu1gEVe+ebjwPo0Idq/IKgs+5KWUn/ldoEKAxt9 v0gH6m40CEe6lV42BBXk1iswmJHFzjz6u3dz8WJeVniKKAw4EZe4/dK5G8ojNgQcf5bFV7HPTocMz FRHhWy3lLlOb4yiDPjwEdlUOmcfervjPiwKOo/hNT1/kJeAIOraz7R90MEtexL0+nrwDPIsroABBw a8+6MIDkfZ3pw9he6gXBhkSvxzO/X3d6MjWQdVMLhALgQIs7r6ernzxbx8a/z44s7fjXse1gy8YF+ meEZ4UQQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1j9UTC-0000HA-SQ; Wed, 04 Mar 2020 13:53:55 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 767C630066E; Wed, 4 Mar 2020 14:51:53 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DF7D423D4FA1C; Wed, 4 Mar 2020 14:53:51 +0100 (CET) Date: Wed, 4 Mar 2020 14:53:51 +0100 From: Peter Zijlstra To: syzbot Cc: acme@kernel.org, alexander.shishkin@linux.intel.com, andriin@fb.com, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, jolsa@redhat.com, kafai@fb.com, linux-kernel@vger.kernel.org, mark.rutland@arm.com, mingo@redhat.com, namhyung@kernel.org, netdev@vger.kernel.org, songliubraving@fb.com, syzkaller-bugs@googlegroups.com, yhs@fb.com Subject: Re: WARNING: locking bug in __perf_event_task_sched_in Message-ID: <20200304135351.GN2596@hirez.programming.kicks-ass.net> References: <0000000000005c967305a006d54d@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000000000005c967305a006d54d@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Mar 04, 2020 at 04:48:13AM -0800, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: f8788d86 Linux 5.6-rc3 > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13bcd8f9e00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5d2e033af114153f > dashboard link: https://syzkaller.appspot.com/bug?extid=3daecb3e8271380aeb51 > compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+3daecb3e8271380aeb51@syzkaller.appspotmail.com > > ------------[ cut here ]------------ > DEBUG_LOCKS_WARN_ON(1) > WARNING: CPU: 0 PID: 22488 at kernel/locking/lockdep.c:167 hlock_class kernel/locking/lockdep.c:167 [inline] > WARNING: CPU: 0 PID: 22488 at kernel/locking/lockdep.c:167 __lock_acquire+0x18b8/0x1bc0 kernel/locking/lockdep.c:3950 Something went sideways bad, could be you've overflowed lockdep_depth. For some reason the check: if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) is rather late.. Dunno, most times I've hit lockdep errors like this, something else was screwy and we're just the ones to trip over it.