From owner-svn-src-all@freebsd.org Wed Mar 21 20:28:04 2018 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A4F33F6460C; Wed, 21 Mar 2018 20:28:04 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 2392F863A1; Wed, 21 Mar 2018 20:28:04 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id w2LKRqEf020067 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 21 Mar 2018 22:27:55 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua w2LKRqEf020067 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id w2LKRqBW020066; Wed, 21 Mar 2018 22:27:52 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 21 Mar 2018 22:27:52 +0200 From: Konstantin Belousov To: Bruce Evans Cc: Warner Losh , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r331298 - head/sys/dev/syscons Message-ID: <20180321202752.GO76926@kib.kiev.ua> References: <201803211447.w2LElDcK091988@repo.freebsd.org> <20180322024846.S4293@besplex.bde.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180322024846.S4293@besplex.bde.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on tom.home X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Mar 2018 20:28:04 -0000 On Thu, Mar 22, 2018 at 04:53:22AM +1100, Bruce Evans wrote: > Serial console drivers with fast interrupt handlers have much more > broken locking for ddb special keys. It is invalid to either drop locks > or call the "any" function from a fast interrupt handler, but buggy > serial console drivers calls kbd_alt_break(), and that now calls > shutdown_nice() and other functions that cannot be called from a fast > interrupt handler. ddb keys supply most of the shutdown_nice() > functionality for serial consoles, and there are no escape sequence to > get this without ddb or maybe another debugger, so these bugs don't > affect most users. > > Handling this correctly requires much the same fix as an unsafe signal > handler, and fixes have much the same problems -- not much more than > setting a flag is safe, and the flag might never be looked at if the > system is in a bad state. However, if a nice shutdown is possible then > the sytem must be in a good enough state to poll for flags. Are you saying that fast interrupt handlers call shutdown_nice() ? This is the quite serious bug on its own. To fix it, shutdown_nice() should use a fast taskqueue to schedule the task which would lock the process and send the signal.