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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 5A581C04EBD for ; Tue, 16 Oct 2018 13:24:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1984320869 for ; Tue, 16 Oct 2018 13:24:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1984320869 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727059AbeJPVPB (ORCPT ); Tue, 16 Oct 2018 17:15:01 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:58133 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726760AbeJPVPA (ORCPT ); Tue, 16 Oct 2018 17:15:00 -0400 Received: from hsi-kbw-5-158-153-52.hsi19.kabel-badenwuerttemberg.de ([5.158.153.52] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1gCPKR-0005u6-47; Tue, 16 Oct 2018 15:24:07 +0200 Date: Tue, 16 Oct 2018 15:24:06 +0200 (CEST) From: Thomas Gleixner To: syzbot cc: Borislav Petkov , "H. Peter Anvin" , LKML , mingo@redhat.com, nstange@suse.de, syzkaller-bugs@googlegroups.com, x86@kernel.org, Peter Zijlstra Subject: Re: INFO: rcu detected stall in do_idle In-Reply-To: <000000000000a4ee200578172fde@google.com> Message-ID: References: <000000000000a4ee200578172fde@google.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 13 Oct 2018, syzbot wrote: > syzbot found the following crash on: > > HEAD commit: 6b3944e42e2e afs: Fix cell proc list > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1545a479400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=88e9a8a39dc0be2d > dashboard link: https://syzkaller.appspot.com/bug?extid=385468161961cee80c31 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14825d5e400000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=122cc531400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+385468161961cee80c31@syzkaller.appspotmail.com > > sshd (5193) used greatest stack depth: 15496 bytes left > sched: DL replenish lagged too much > hrtimer: interrupt took 417330 ns > rcu: INFO: rcu_sched detected stalls on CPUs/tasks: It does reproduce here but with a kworker stall. Looking at the reproducer: *(uint32_t*)0x20000000 = 0; *(uint32_t*)0x20000004 = 6; *(uint64_t*)0x20000008 = 0; *(uint32_t*)0x20000010 = 0; *(uint32_t*)0x20000014 = 0; *(uint64_t*)0x20000018 = 0x9917; *(uint64_t*)0x20000020 = 0xffff; *(uint64_t*)0x20000028 = 0; syscall(__NR_sched_setattr, 0, 0x20000000, 0); which means: struct sched_attr { .size = 0, .policy = 6, .flags = 0, .nice = 0, .priority = 0, .deadline = 0x9917, .runtime = 0xffff, .period = 0, } policy 6 is SCHED_DEADLINE That makes the thread hog the CPU and prevents all kind of stuff to run. Peter, is that expected behaviour? Thanks, tglx