From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15527 invoked by alias); 16 Oct 2018 03:38:43 -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 15503 invoked by uid 89); 16 Oct 2018 03:38:42 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-26.2 required=5.0 tests=BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,RCVD_IN_DNSWL_NONE,SPF_SOFTFAIL autolearn=ham version=3.3.2 spammy=ours, owns, rolling, HContent-Transfer-Encoding:8bit X-HELO: barracuda.ebox.ca Received: from barracuda.ebox.ca (HELO barracuda.ebox.ca) (96.127.255.19) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 16 Oct 2018 03:38:38 +0000 Received: from smtp.ebox.ca (smtp.electronicbox.net [96.127.255.82]) by barracuda.ebox.ca with ESMTP id Enr5r0nmTc2FMsBy (version=TLSv1 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 15 Oct 2018 23:38:36 -0400 (EDT) Received: from simark.lan (unknown [192.222.164.54]) by smtp.ebox.ca (Postfix) with ESMTP id CFE0B441D64; Mon, 15 Oct 2018 23:38:36 -0400 (EDT) From: Simon Marchi To: gdb-patches@sourceware.org Cc: Simon Marchi Subject: [PATCH 3/3] Avoid GDB SIGTTOU on catch exec + set follow-exec-mode new (PR 23368) Date: Tue, 16 Oct 2018 03:38:00 -0000 Message-Id: <20181016033835.17594-3-simon.marchi@polymtl.ca> In-Reply-To: <20181016033835.17594-1-simon.marchi@polymtl.ca> References: <20181016033835.17594-1-simon.marchi@polymtl.ca> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-IsSubscribed: yes X-SW-Source: 2018-10/txt/msg00338.txt.bz2 Here's a summary of PR 23368: #include int main (void) { char *exec_args[] = { "/bin/ls", NULL }; execve (exec_args[0], exec_args, NULL); } $ gdb -nx t -ex "catch exec" -ex "set follow-exec-mode new" -ex run ... [1] + 13146 suspended (tty output) gdb -q -nx t -ex "catch exec" -ex "set follow-exec-mode new" -ex run $ Here's what happens: when the inferior execs with "follow-exec-mode new", we first "mourn" it before creating the new one. This ends up calling inflow_inferior_exit, which sets the per-inferior terminal state to "is_ours": inf->terminal_state = target_terminal_state::is_ours; At this point, the inferior's terminal_state is is_ours, while the "reality", tracked by gdb_tty_state, is is_inferior (GDB doesn't own the terminal). Later, we continue processing the exec inferior event and decide we want to stop (because of the "catch exec") and call target_terminal::ours to make sure we own the terminal. However, we don't actually go to the target backend to change the settings, because the core thinks that no inferior owns the terminal (inf->terminal_state is target_terminal_state::is_ours, as checked in target_terminal_is_ours_kind, for both inferiors). When something in readline tries to mess with the terminal settings, it generates a SIGTTOU. This patch manages to fix this particular case by calling target_terminal::ours() in inflow_inferior_exit. This makes so that inflow actually changes the terminal settings so that GDB owns it, which avoids the SIGTTOU later. The buildbot doesn't complain, but I am not sure this is the most bestest way to fix this, maybe it's just papering over the actual problem or introduces some latent bug. In particular, I am not sure if this is correct in case we have multiple inferiors sharing the same terminal. But I thought I would still submit this patch to get the ball rolling. gdb/ChangeLog: PR gdb/23368 * inflow.c (inflow_inferior_exit): Update doc. Call target_terminal::ours. --- gdb/inflow.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/gdb/inflow.c b/gdb/inflow.c index e355f4aa9fc5..95e195167ef7 100644 --- a/gdb/inflow.c +++ b/gdb/inflow.c @@ -653,18 +653,15 @@ get_inflow_inferior_data (struct inferior *inf) return info; } -/* This is a "inferior_exit" observer. Releases the TERMINAL_INFO member - of the inferior structure. This field is private to inflow.c, and - its type is opaque to the rest of GDB. PID is the target pid of - the inferior that is about to be removed from the inferior - list. */ +/* This is a "inferior_exit" observer. Releases the terminal info associated + to INF. */ static void inflow_inferior_exit (struct inferior *inf) { struct terminal_info *info; - inf->terminal_state = target_terminal_state::is_ours; + target_terminal::ours (); info = (struct terminal_info *) inferior_data (inf, inflow_inferior_data); if (info != NULL) -- 2.19.1