From: Yao Qi <qiyaoltc@gmail.com>
To: Pedro Alves <palves@redhat.com>
Cc: Yao Qi <qiyaoltc@gmail.com>, gdb-patches@sourceware.org
Subject: Re: [PATCH] Fix fail in gdb.base/interrupt-noterm.exp
Date: Mon, 25 Jan 2016 09:30:00 -0000 [thread overview]
Message-ID: <86powqqa57.fsf@gmail.com> (raw)
In-Reply-To: <56A26849.9070206@redhat.com> (Pedro Alves's message of "Fri, 22 Jan 2016 17:35:05 +0000")
Pedro Alves <palves@redhat.com> writes:
> If 1. is followed by 3., then the \\003 is always read by gdb
s/ready by/sent by/ ?
> after the vCont;c. We call enable_async_io before reaching
> mywait. Since we're in all-stop, that means we'll block
Although we call enable_async_io earlier, so the window between received
vCont;c and calling enable_async_io is tiny, it is still possible that
\\003 arrives at that period.
> inside mywait -> waitpid, all the while \\003 is already available to
> read in the socket. Since we're blocked in waitpid, we won't see
> the \\003 until after the next time the program happens to stop.
>
> Agree?
Yes, I agree.
>
> It still seems to me like a gdbserver bug.
>
> I think that after calling enable_async_io, we need to check whether
> input is already pending from GDB, and if so, process it immediately -- we
> know the only input coming from GDB at this point is a \\003. IOW, I think
> we need to call input_interrupt after calling enable_async_io. input_interrupt
> already uses select before reading, so it handles the case of there
> being no input available without blocking.
>
> However, we need to be careful, because a SIGIO can race with calling
> input_interrupt from mainline code...
What you mean here is that we can call input_interrupt after calling
enable_async_io, but meanwhile, \\0003 arrives, and input_interrupt is
invoked as a SIGIO handler, so there is a race. Is it correct?
I agree your next email about the approach of block/unblock SIGIO is
better. I'll give a fix that way.
--
Yao (齐尧)
next prev parent reply other threads:[~2016-01-25 9:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-22 16:29 Yao Qi
2016-01-22 16:47 ` Pedro Alves
2016-01-22 17:14 ` Yao Qi
2016-01-22 17:35 ` Pedro Alves
2016-01-22 18:30 ` Pedro Alves
2016-01-25 9:30 ` Yao Qi [this message]
2016-01-25 10:43 ` Pedro Alves
2016-01-26 9:59 ` [PATCH 0/2 V2] Fix a " Yao Qi
2016-01-26 9:59 ` [PATCH 2/2] [GDBserver] Block and unblock SIGIO Yao Qi
2016-01-26 12:01 ` Pedro Alves
2016-01-26 13:55 ` Yao Qi
2016-01-26 9:59 ` [PATCH 1/2] [GDBserver] Check input interrupt after reading in a packet Yao Qi
2016-01-26 11:42 ` Pedro Alves
2016-01-26 13:53 ` Yao Qi
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