From: Pedro Alves <palves@redhat.com>
To: Andreas Arnez <arnez@linux.vnet.ibm.com>
Cc: jan.kratochvil@redhat.com, gdb@sourceware.org
Subject: Re: Strange behavior of sigstep-threads.exp?
Date: Wed, 21 Nov 2012 19:19:00 -0000 [thread overview]
Message-ID: <50AD2913.1090603@redhat.com> (raw)
In-Reply-To: <874nki6bfq.fsf@linux.vnet.ibm.com>
On 11/21/2012 06:46 PM, Andreas Arnez wrote:
> Pedro Alves <palves@redhat.com> writes:
>
>> linux-nat.c always gives preference to a SIGTRAP over other signals,
>> so it's unexpected that a trap could be lost. Maybe while GDB goes
>> about stopping all threads with SIGSTOP (in effect, only the
>> single-stepped thread), the single step has actually completed, but
>> the kernel manages to report the SIGSTOP first, for some bizarre
>> reason? IOW, the kernel loses the trap.
>
> Right, the kernel loses the trap.
Great (that GDB isn't at fault). :-)
> While processing the SIGUSR1 from thread #2, GDB stops all other threads
> with SIGSTOP -- in this case the single-stepped thread #1. Now if the
> SIGSTOP is sent after thread #1 has received the single-step exception,
> but before the kernel has decided what signals to present, the kernel
> suppresses the SIGTRAP and just delivers the SIGSTOP instead.
>
> Discussed this with the s390 kernel maintainer. A kernel patch is on
> the way.
Thanks.
--
Pedro Alves
prev parent reply other threads:[~2012-11-21 19:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-08 15:51 Andreas Arnez
2012-11-12 16:38 ` Pedro Alves
2012-11-13 15:21 ` Andreas Arnez
2012-11-14 16:15 ` Pedro Alves
2012-11-21 18:47 ` Andreas Arnez
2012-11-21 19:19 ` Pedro Alves [this message]
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