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,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 1FB1CC46475 for ; Tue, 23 Oct 2018 12:12:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF2C420671 for ; Tue, 23 Oct 2018 12:12:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="HFtJemb+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF2C420671 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 S1728090AbeJWUfs (ORCPT ); Tue, 23 Oct 2018 16:35:48 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:39540 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727264AbeJWUfs (ORCPT ); Tue, 23 Oct 2018 16:35:48 -0400 Received: by mail-pl1-f196.google.com with SMTP id e67-v6so528415plb.6; Tue, 23 Oct 2018 05:12:35 -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=X+VDBCcN50SuGfbTBlLF8lQKLFDbCRL6cREZHVdGokM=; b=HFtJemb+dlhgLRKQLJZzGHvFBTrUDNz9n9v2BSpD5wr7uSoCUa/g+tc66dxexLXQ6F fd00nMEnBnsqPYKUkxftC4woKBRn53zXlT0qRPT0T+7Sj5mAPPWP7C7c/7PO2Ap7XR4/ lVRXbLDLwg2yNKN3vEQiqDMz+fDBmsCuo3dETstnL/Cn0bSb/DkLJvGWkC3s4C6RZ7ra h/bqWunOYG2gteq/dGSCKFuEViZA38CWHbC6oWc80Is4pD22pGEPtZc3I+Dc1yJljX/e /rTLMCICtlFbqiFkTVjE0DCwV7VCxVoe25jTVIWRiljNMBAwc8KGT/RyhbA5vQplgSgX wcwQ== 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=X+VDBCcN50SuGfbTBlLF8lQKLFDbCRL6cREZHVdGokM=; b=L2jrozr20gcryhdoqo6fdxwFO4xgS40vfhrFFAztv2Pn/EIFUB9lXEKh/ij0Ln60HE cMcaZWdPYFI2fJ5VPyhJr+Lg1Ayukw/xMyIglrFAgoPqtPMuQwWmAUhBHNdywFPANaYH kVxAXnYuBf8/0lpoJr/AyNUYXBx03TSBGUZ7K3Bc35u2uaepRqgFa9oQrlSUNELnlgh9 xDESyOJBQfQBjvGOtL9xdl5w98X6VmE+QNSRiindRRVZnEth213gjHbKt94BK+qJcMIO 1Ju10ZklieIKQTuHGfNBQKDyfiIgZLhdTwSmofL4IwOkHvLCmkHOqs5DGViMJCV2pm4/ Jseg== X-Gm-Message-State: AGRZ1gIwHA3BpuhMC5xDuFttPLeWy3GfOZrDvrKPMMEVFZKw7uapl0sw qGL7043bfkigGV7xGmfuSM4= X-Google-Smtp-Source: AJdET5cyIDQ2qpJM4JwoE4Pkl5zPJMxMpkyrCvAedyhh47sGUGBpgsDf9urt93k+Uqc78zOuI/37+A== X-Received: by 2002:a17:902:2924:: with SMTP id g33-v6mr11643797plb.76.1540296754637; Tue, 23 Oct 2018 05:12:34 -0700 (PDT) Received: from localhost ([175.223.11.183]) by smtp.gmail.com with ESMTPSA id p1-v6sm1858032pfj.72.2018.10.23.05.12.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 23 Oct 2018 05:12:33 -0700 (PDT) Date: Tue, 23 Oct 2018 21:12:30 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: linux-kernel@vger.kernel.org, Steven Rostedt , Daniel Wang , Peter Zijlstra , Andrew Morton , Linus Torvalds , Greg Kroah-Hartman , Alan Cox , Jiri Slaby , Peter Feiner , linux-serial@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: Re: [RFC][PATCHv2 1/4] panic: avoid deadlocks in re-entrant console drivers Message-ID: <20181023121057.GC10251@jagdpanzerIV> References: <20181016050428.17966-1-sergey.senozhatsky@gmail.com> <20181016050428.17966-2-sergey.senozhatsky@gmail.com> <20181023110751.un2u67bc7dpo4ska@pathway.suse.cz> <20181023115433.GA10251@jagdpanzerIV> <20181023120441.GB10251@jagdpanzerIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181023120441.GB10251@jagdpanzerIV> 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 (10/23/18 21:04), Sergey Senozhatsky wrote: > > Seems that s390 is the only arch which defines its own bust_spinlocks(). > Not sure why... Just to play games with console_loglevel? > > --- > > void bust_spinlocks(int yes) > { > if (yes) { > oops_in_progress = 1; > } else { > int loglevel_save = console_loglevel; > console_unblank(); > oops_in_progress = 0; > /* > * OK, the message is on the console. Now we call printk() > * without oops_in_progress set so that printk will give klogd > * a poke. Hold onto your hats... > */ > console_loglevel = 15; > printk(" "); > console_loglevel = loglevel_save; > } > } > > --- > > The "printk(" "); without oops_in_progress" part is a bit worrisome. > This thing technically can deadlock. Unless s390 has no NMI panic(). And console_unblank() is not guaranteed to print anything (unlike console_flush_on_panic(), but oops is not panic() yet, so we can't replace it with flush_on_panic()) - console_sem can be locked, so console_unblank() would do nothing. That printk(" ") probably wants to be printk_deferred(" "). -ss