From: Pedro Alves <palves@redhat.com>
To: Doug Evans <dje@google.com>
Cc: gdb-patches <gdb-patches@sourceware.org>
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]]
Date: Wed, 30 Jul 2014 12:46:00 -0000 [thread overview]
Message-ID: <53D8E725.8080902@redhat.com> (raw)
In-Reply-To: <CADPb22TxuPBD9JPwuaF_JpeF2E0QfiLvVt_ee19Y4XhJFWyKKw@mail.gmail.com>
On 07/29/2014 11:03 PM, Doug Evans wrote:
> A related issue (or the same one if one prefers):
>
> post_create_inferior does this:
>
> /* Be sure we own the terminal in case write operations are performed. */
> target_terminal_ours ();
Yeah.
As I mentioned before, when I wrote a test that sends a ctrl-c right
after "attach", which triggered the issue mentioned in the new
comment,
- installs a SIGINT handler that forwards SIGINT to the inferior.
Otherwise a Ctrl-C pressed just while waiting for the initial
stop would end up as a spurious Quit.
it tripped on a set of other races.
This call was one of them. We should actually be calling
target_terminal_ours_for_output, not target_terminal_ours, so
that stdin/ctrl-c is still redirected to the inferior. As is,
IIRC, if a ctrl-c arrives after than target_terminal_ours and before
the next target_terminal_inferior, we end up in the prompt, with
a Quit, but with the target still running.
I gave up fixing those at the time, as they're orthogonal to
sync/async.
>
> but post_create_inferior is called *after* target_post_attach
> in attach_command_post_wait:
>
> /* Take any necessary post-attaching actions for this platform. */
> target_post_attach (ptid_get_pid (inferior_ptid));
>
> post_create_inferior (¤t_target, from_tty);
>
> What if target_post_attach does some writes?
Something should call target_terminal_ours_for_output before.
> Seems like it can, e.g., some of the ptrace checking stuff may print a warning.
> Plus attach_command_post_wait calls some other stuff before
> post_create_inferior that could cause some writes to the terminal.
>
> Question: Is there a specific terminal state that needs to be in
> effect when attach_command_post_wait returns?
> Or can we just call target_terminal_ours at its start?
I think we can.
> [and leave it to other code to switch back to target_terminal_inferior
> as needed - e.g. proceed calls resume which will call
> target_terminal_inferior]
Even with that, it'll still be possible to have a ctrl-c pressed after
to_attach is called, and before target_terminal_inferior is called
(and therefore set_sigint_trap is called, which sets up ctrl-c
forwarding).
When I last looked at this, it seemed to be that ideally, we should
only have a single SIGINT handler, which just records that a ctrl-c was
pressed, and then the event loop decides whether a ctrl-c is a Quit or
whether it should be forwarded to the inferior, depending on whether the
target is running on the foreground, or not.
--
Thanks,
Pedro Alves
next prev parent reply other threads:[~2014-07-30 12:38 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-23 20:59 [PATCH v6 0/2] enable target-async by default Pedro Alves
2014-05-23 20:59 ` [PATCH v6 2/2] enable target async by default; separate MI and target notions of async Pedro Alves
2014-05-24 7:03 ` Eli Zaretskii
2014-05-29 13:49 ` Pedro Alves
2014-07-30 18:40 ` Doug Evans
2014-05-23 20:59 ` [PATCH v6 1/2] Make display_gdb_prompt CLI-only Pedro Alves
2014-05-29 13:44 ` [pushed] Re: [PATCH v6 0/2] enable target-async by default Pedro Alves
2014-07-01 16:28 ` Regression for attach from stdin [Re: [pushed] Re: [PATCH v6 0/2] enable target-async by default] Jan Kratochvil
2014-07-02 8:59 ` Mark Wielaard
2014-07-02 9:16 ` Pedro Alves
2014-07-03 15:39 ` Pedro Alves
2014-07-04 13:48 ` [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]] Pedro Alves
2014-07-04 21:13 ` Mark Wielaard
2014-07-07 16:39 ` Doug Evans
2014-07-08 15:24 ` Pedro Alves
2014-07-09 16:37 ` Doug Evans
2014-07-09 17:09 ` [pushed+7.8] " Pedro Alves
2014-07-29 22:03 ` Doug Evans
2014-07-29 23:10 ` Doug Evans
2014-07-30 12:46 ` Pedro Alves [this message]
2014-07-30 12:38 ` Pedro Alves
2014-07-30 16:59 ` Doug Evans
2014-08-21 16:34 ` [PUSHED] infcmd.c: Remove stale TODO Pedro Alves
2014-09-03 7:59 ` Regression: GDB stopped on run with attached process (PR 17347) [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]]] Jan Kratochvil
2014-09-03 20:11 ` Regression: GDB stopped on run with attached process (PR 17347) [Re: [pushed+7.8] Re: [PATCH] Fix "attach" command vs user input race Pedro Alves
2014-09-07 19:28 ` Jan Kratochvil
2014-09-08 16:19 ` [PATCH 1/2] testsuite: refactor spawn and wait for attach (was: Re: Regression: GDB stopped on run with attached process) Pedro Alves
2014-09-09 17:29 ` Jan Kratochvil
2014-09-09 17:35 ` [PATCH 1/2] testsuite: refactor spawn and wait for attach Pedro Alves
2014-09-10 21:25 ` Pedro Alves
2014-09-11 12:34 ` Pedro Alves
2014-09-08 16:27 ` Regression: GDB stopped on run with attached process (PR 17347) [Re: [pushed+7.8] Re: [PATCH] Fix "attach" command vs user input race Pedro Alves
2014-09-09 18:25 ` Jan Kratochvil
2014-09-11 12:36 ` Pedro Alves
2014-09-12 7:34 ` [testsuite patch] runaway attach processes [Re: Regression: GDB stopped on run with attached process (PR 17347)] Jan Kratochvil
2014-09-12 10:14 ` Pedro Alves
2014-09-12 11:40 ` [commit] " Jan Kratochvil
2014-07-07 17:02 ` [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]] Jan Kratochvil
2014-10-05 14:00 ` Crash regression for annota1.exp w/vDSO debuginfo [Re: [pushed] Re: [PATCH v6 0/2] enable target-async by default] Jan Kratochvil
2014-10-05 14:14 ` Jan Kratochvil
2014-10-05 16:43 ` Jan Kratochvil
2014-10-09 15:48 ` Pedro Alves
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