From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26631 invoked by alias); 30 Jul 2014 12:05:26 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 26619 invoked by uid 89); 30 Jul 2014 12:05:25 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.2 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 30 Jul 2014 12:05:24 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s6UC5KBn015247 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 30 Jul 2014 08:05:21 -0400 Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s6UC5Jca008960; Wed, 30 Jul 2014 08:05:19 -0400 Message-ID: <53D8DF7E.6070506@redhat.com> Date: Wed, 30 Jul 2014 12:38:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Doug Evans CC: gdb-patches Subject: Re: [pushed+7.8] Re: [PATCH] Fix "attach" command vs user input race [Re: Regression for attach from stdin [Re: [pushed] Re: [PATCH v6 0/2] enable target-async by default]] References: <1400878753-24688-1-git-send-email-palves@redhat.com> <538739A2.2050105@redhat.com> <20140701162830.GA25877@host2.jankratochvil.net> <1404291574.3766.35.camel@bordewijk.wildebeest.org> <53B3CDCC.9050502@redhat.com> <53B57911.10304@redhat.com> <53B6B0B8.2050702@redhat.com> <21434.52532.737427.778289@ruffy.mtv.corp.google.com> <53BC0D0B.7040001@redhat.com> <21437.28600.751354.629884@ruffy.mtv.corp.google.com> <53BD7749.5000800@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SW-Source: 2014-07/txt/msg00784.txt.bz2 On 07/29/2014 10:48 PM, Doug Evans wrote: > On Wed, Jul 9, 2014 at 10:09 AM, Pedro Alves wrote: >> On 07/09/2014 05:37 PM, Doug Evans wrote: >> >>> spurious change >> >> Fixed. >> >>> I like this a lot better. Thanks. >>> The patch is ok with me, modulo removing the spurious change. >> >> Here's what I pushed to both master and gdb-7.8-branch. >> >> Thanks. >> >> ------------- >> From 1fe2833b6dd03602ba86aa334e81466ea9abe66a Mon Sep 17 00:00:00 2001 >> From: Pedro Alves >> Date: Wed, 9 Jul 2014 17:52:58 +0100 >> Subject: [PATCH] Fix "attach" command vs user input race >> >> On async targets, a synchronous attach is done like this: >> >> #1 - target_attach is called (PTRACE_ATTACH is issued) >> #2 - a continuation is installed >> #3 - we go back to the event loop >> #4 - target reports stop (SIGSTOP), event loop wakes up, and >> attach continuation is called >> #5 - among other things, the continuation calls >> target_terminal_inferior, which removes stdin from the event >> loop >> >> Note that in #3, GDB is still processing user input. If the user is >> fast enough, e.g., with something like: >> >> echo -e "attach PID\nset xxx=1" | gdb >> >> ... then the "set" command is processed before the attach completes. >> >> We get worse behavior even, if input is a tty and therefore >> readline/editing is enabled, with e.g.,: >> >> (gdb) attach PID\nset xxx=1 >> >> we then crash readline/gdb, with: >> >> Attaching to program: attach-wait-input, process 14537 >> readline: readline_callback_read_char() called with no handler! >> Aborted >> $ >> >> Fix this by calling target_terminal_inferior before #3 above. >> >> The test covers both scenarios by running with editing/readline forced >> to both on and off. >> >> gdb/ >> 2014-07-09 Pedro Alves >> >> * infcmd.c (attach_command_post_wait): Don't call >> target_terminal_inferior here. >> (attach_command): Call it here instead. >> >> gdb/testsuite/ >> 2014-07-09 Pedro Alves >> >> * gdb.base/attach-wait-input.exp: New file. >> * gdb.base/attach-wait-input.c: New file. > > Hi. > > Is this TODO still needed after this patch? > > infcmd.c: > > /* > * TODO: > * Should save/restore the tty state since it might be that the > * program to be debugged was started on this tty and it wants > * the tty in some state other than what we want. If it's running > * on another terminal or without a terminal, then saving and > * restoring the tty state is a harmless no-op. > * This only needs to be done if we are attaching to a process. > */ > As usual, git blame/log is your friend... That's been in place for over 20 years. In bd5635a1 (1991), we see: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /* * TODO: * Should save/restore the tty state since it might be that the * program to be debugged was started on this tty and it wants * the tty in some state other than what we want. If it's running * on another terminal or without a terminal, then saving and * restoring the tty state is a harmless no-op. * This only needs to be done if we are attaching to a process. */ /* * attach_command -- * takes a program started up outside of gdb and ``attaches'' to it. * This stops it cold in its tracks and allows us to start tracing it. * For this to work, we must be able to send the process a * signal and we must have the same effective uid as the program. */ void attach_command (args, from_tty) char *args; int from_tty; { target_attach (args, from_tty); } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ So clearly the TODO has been stale for a long while. We've been saving/restoring the tty state way before my patch. Thanks, Pedro Alves