From: Pedro Alves <palves@redhat.com>
To: Yao Qi <qiyaoltc@gmail.com>, gdb-patches@sourceware.org
Subject: Re: exceptions.KeyboardInterrupt is thrown in gdb.base/random-signal.exp
Date: Wed, 25 Nov 2015 16:26:00 -0000 [thread overview]
Message-ID: <5655E141.7030503@redhat.com> (raw)
In-Reply-To: <86ziy2xdt7.fsf@gmail.com>
On 11/25/2015 04:07 PM, Yao Qi wrote:
> Hi,
> I am fixing a fail in gdb.base/random-signal.exp like this,
>
> Continuing.^M
> PASS: gdb.base/random-signal.exp: continue
> ^CPython Exception <type 'exceptions.KeyboardInterrupt'> <type 'exceptions.KeyboardInterrupt'>: ^M
> FAIL: gdb.base/random-signal.exp: stop with control-c (timeout)
>
> I only see this fail out of 15~20 runs each time. Is it because GDB
> received SIGINT before async_handle_remote_sigint is installed? so
> handle_sigint is still the SIGINT handler, set_quit_flag will call
> python stuff, and KeyboardInterrupt is raised as a result.
>
> In the test, we've already been aware of that the signal handler isn't
> ready, so "Continuing" is consumed and ctrl-c is delayed in 500ms.
>
> # For this to work we must be sure to consume the "Continuing."
> # message first, or GDB's signal handler may not be in place.
> after 500 {send_gdb "\003"}
>
> After I read the tcl manul about "after", I feel the usage of "after"
> above isn't 100% correct. As the manual says, the "after" command
> returns immediately, and the tcl command {send_gdb "\003"} will be
> executed 500 ms later. It is an asynchronous flavour, but what we want is
> a synchronous operation, like this,
>
> after 500
> send_gdb "\003"
>
> with this change, I don't see the timeout fail again. Is it a fix or a
> hack?
>
Seems like a hack -- I don't see how that can make a difference. In both
cases, we send \003 after 500ms.
The test sets a software watchpoint, and resumes the target. That means
the program will be constantly single-stepping, and gdb will be evaluating
the watched expression at each single-step. I'd suspect that the problem
is likely that while the program is stopped to evaluate the watched
expression, something is calling target_terminal_ours, which restores
handle_sigint as SIGINT handler. Then somehow you're unlucky to manage to
ctrl-c at that exact time. The fix in that case is likely to be to call
target_terminal_ours_for_output instead, which doesn't touch the SIGINT
handler.
Thanks,
Pedro Alves
next prev parent reply other threads:[~2015-11-25 16:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-25 16:07 Yao Qi
2015-11-25 16:26 ` Pedro Alves [this message]
2015-11-25 17:16 ` Yao Qi
2015-12-01 17:15 ` Yao Qi
2015-12-03 12:47 ` Pedro Alves
2015-12-03 17:09 ` Yao Qi
2015-12-03 17:19 ` Pedro Alves
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5655E141.7030503@redhat.com \
--to=palves@redhat.com \
--cc=gdb-patches@sourceware.org \
--cc=qiyaoltc@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).