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_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,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 41E17ECDE43 for ; Fri, 19 Oct 2018 11:40:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1599205F4 for ; Fri, 19 Oct 2018 11:40:14 +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="WJKPQP7z" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1599205F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1727246AbeJSTpy (ORCPT ); Fri, 19 Oct 2018 15:45:54 -0400 Received: from merlin.infradead.org ([205.233.59.134]:37232 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726678AbeJSTpy (ORCPT ); Fri, 19 Oct 2018 15:45:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=eA6QITRghzqA59wlagXhUriGbJdvtkuWgn7JL2XOxUE=; b=WJKPQP7ztppitf237SqKhk/49 B/78PTKXGgGDZstbtIJtNbWF/NC3duKdt+Z7Wt7uSh6/hLqgsb+mDAgHcAfYh5G54z0EqQUTNKcQj SYiOgBAro6cKhatxhP+zw+P88ZV1ViwJ+EuWS9NRm8dMymeloJOJ+GDq4sriFusjlCvxhabFTN97t XPQd9R+sH83dT/ZiRkEiQqCBQy4yx5L1JpdalFZBFqHO+drJWKtaR5yhJm+GE/XYlWMub0C+PD5wc nt/OPGUWu9FuoqRiP0ozRLT5/52G0OMJnVzhpSMh5tzwMt7L0Bm/b6w/YxET/RmyYETdhbhZe9SJq meLtjJdNA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gDT84-0004Xo-O9; Fri, 19 Oct 2018 11:39:45 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 57D3E2029856B; Fri, 19 Oct 2018 13:39:42 +0200 (CEST) Date: Fri, 19 Oct 2018 13:39:42 +0200 From: Peter Zijlstra To: luca abeni Cc: Juri Lelli , Thomas Gleixner , Juri Lelli , syzbot , Borislav Petkov , "H. Peter Anvin" , LKML , mingo@redhat.com, nstange@suse.de, syzkaller-bugs@googlegroups.com, henrik@austad.us, Tommaso Cucinotta , Claudio Scordino , Daniel Bristot de Oliveira Subject: Re: INFO: rcu detected stall in do_idle Message-ID: <20181019113942.GH3121@hirez.programming.kicks-ass.net> References: <000000000000a4ee200578172fde@google.com> <20181016140322.GB3121@hirez.programming.kicks-ass.net> <20181016144045.GF9130@localhost.localdomain> <20181016153608.GH9130@localhost.localdomain> <20181018082838.GA21611@localhost.localdomain> <20181018122331.50ed3212@luca64> <20181018104713.GC21611@localhost.localdomain> <20181018130811.61337932@luca64> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181018130811.61337932@luca64> 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 Thu, Oct 18, 2018 at 01:08:11PM +0200, luca abeni wrote: > Ok, I see the issue now: the problem is that the "while (dl_se->runtime > <= 0)" loop is executed at replenishment time, but the deadline should > be postponed at enforcement time. > > I mean: in update_curr_dl() we do: > dl_se->runtime -= scaled_delta_exec; > if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) { > ... > enqueue replenishment timer at dl_next_period(dl_se) > But dl_next_period() is based on a "wrong" deadline! > > > I think that inserting a > while (dl_se->runtime <= -pi_se->dl_runtime) { > dl_se->deadline += pi_se->dl_period; > dl_se->runtime += pi_se->dl_runtime; > } > immediately after "dl_se->runtime -= scaled_delta_exec;" would fix the > problem, no? That certainly makes sense to me. The only remaining issue would then be placing a limit on the amount of times we can take that loop; which, as you propose in a later email; can be done separately as a limit on runtime.