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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 01DF3C04EBD for ; Tue, 16 Oct 2018 14:41:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF03920881 for ; Tue, 16 Oct 2018 14:41:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DtHQafuo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF03920881 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com 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 S1727158AbeJPWcT (ORCPT ); Tue, 16 Oct 2018 18:32:19 -0400 Received: from mail-ed1-f65.google.com ([209.85.208.65]:33237 "EHLO mail-ed1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726760AbeJPWcT (ORCPT ); Tue, 16 Oct 2018 18:32:19 -0400 Received: by mail-ed1-f65.google.com with SMTP id l14-v6so12603637edq.0 for ; Tue, 16 Oct 2018 07:41:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=8axZzdNvrzI+u2U7+oDvY9j58Np1YM3RjpcEuRDVIkc=; b=DtHQafuoPc7DjasCmVzobJEekwr2igNZxE/S9NeZl6sJaVW3AQklnLiGKdZ9aZ92zb 2BZLPlzKoAx+AxBM8KN9WArM0uwnfRYMnLyWCdJA9ZaT83jwJkEshtKCRw5huwkUvQuz e+nCvLZSsoRRkwvXwW4Asox8kFJbv8jYNq2h+gckswA5wk+pEacXwgxF0bU31ckTN5dn TxNmjJKMJlcmQC0gQj2Itn3KbynqDmEImixhZ2UmVkwTpO25H0kBLqG6Ly/i8tsFe/SC ZXJ2W/ATWrj4L6hQmqwnUx8ZWMJLhm6c/FJ3KK/OhMHAGbXbCo9+l2N6uJkPsz/ojnMQ GUYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=8axZzdNvrzI+u2U7+oDvY9j58Np1YM3RjpcEuRDVIkc=; b=mo9Mqk4xVPD7e6KYMAkOozQ44uWpY20yqTaUaSUJVXTSvkXTNvE3KYl0Jx+IRBkCBh Z0Qc98Wlxj6uqY8pKHO53H+TB/lH03Luo8tfCRzWKOjmMxeXcwR9D1GQARexBqqKhSr8 UNOV1bvDEAG64htkqEsrKZG1Ql19g4dEDOnCu1Qaooa4lIlgwWSwjMAdlnRGvxKdDLna ISbM39AEHAQ/W3Xe8MsGYwql0Ld3ltpt7D7Xz///VY+ptDXfSgZbl7VLWkoA6XDMz+4L Jrjo4X0S8zuoBbF9dzl4j9F0p/26neA1nIA9zHMCXBLdkaiHR9CelE96BrV73QPhk1zP L9XA== X-Gm-Message-State: ABuFfoiGDpS68gwP+VwJXgd4+eGJywpOhuG2IFvBdfFQnEGAdqrG5Xa1 XVVqmorCvT4EA9sSDXsDkp0= X-Google-Smtp-Source: ACcGV62G/mS0znNf8CngBl4BCW3qf1M3FK/+g33m2Y45QLsQLd0/b6Jg0ys0uQ9vsY1Za1+51jYw+g== X-Received: by 2002:a50:abc2:: with SMTP id u60-v6mr31020767edc.185.1539700892076; Tue, 16 Oct 2018 07:41:32 -0700 (PDT) Received: from localhost.localdomain (p200300EF2BD0F03569FD0D231D8C2067.dip0.t-ipconnect.de. [2003:ef:2bd0:f035:69fd:d23:1d8c:2067]) by smtp.gmail.com with ESMTPSA id h21-v6sm7119155eda.23.2018.10.16.07.41.30 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 16 Oct 2018 07:41:31 -0700 (PDT) Date: Tue, 16 Oct 2018 16:41:28 +0200 From: Juri Lelli To: Peter Zijlstra Cc: Thomas Gleixner , syzbot , Borislav Petkov , "H. Peter Anvin" , LKML , mingo@redhat.com, nstange@suse.de, syzkaller-bugs@googlegroups.com, juri.lelli@redhat.com Subject: Re: INFO: rcu detected stall in do_idle Message-ID: <20181016144045.GF9130@localhost.localdomain> References: <000000000000a4ee200578172fde@google.com> <20181016140322.GB3121@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181016140322.GB3121@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/10/18 16:03, Peter Zijlstra wrote: > On Tue, Oct 16, 2018 at 03:24:06PM +0200, Thomas Gleixner wrote: > > 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? > > Sorta, just like FIFO-99 while(1);. Except we should be rejecting the > above configuration, because of the rule: > > runtime <= deadline <= period > > Juri, where were we supposed to check that? Not if period == 0. https://elixir.bootlin.com/linux/latest/source/kernel/sched/deadline.c#L2632 https://elixir.bootlin.com/linux/latest/source/kernel/sched/deadline.c#L2515 Now, maybe we should be checking also against the default 95% cap? Best, - Juri