From: Jan Kratochvil <jan.kratochvil@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
vda.linux@googlemail.com, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org, akpm@linux-foundation.org,
indan@nul.nu
Subject: Re: waitpid(WNOHANG) should report SIGCHLD-notified signals [Re: [PATCH 09/11] job control: reorganize wait_task_stopped()]
Date: Sun, 15 May 2011 19:47:22 +0200 [thread overview]
Message-ID: <20110515174722.GA26361@host1.jankratochvil.net> (raw)
In-Reply-To: <20110515164705.GI23665@htj.dyndns.org>
Hi Tejun,
On Sun, 15 May 2011 18:47:05 +0200, Tejun Heo wrote:
> Hmmm... I could easily be wrong but AFAICS that shouldn't happen. If
> you can reproduce the problem, please let us know.
I was unable to reproduce it before so OK, I will follow now your statement.
> > But if it is a case it should be fixed as there is no later notification when
> > to call waitpid(WNOHANG) again. And sure the debugger cannot busy-loop poll
> > it.
>
> But, the current WNOHANG wait is racy. It's unlikely but definitely
> possible for WNOHANG to fail when it's expected to succeed (not the
> above case but more convoluted ones).
OK, so FYI it breaks current GDB.
> But, just out of curiosity, is there any reason the ptracer itself
> should be doing something other than waitpid() while tracee is
> running? It's not like ptrace requests can be issued during that time
> and sleeping waitpid() is way saner mechanism to wait for tracee
> events than signal.
If the debugger wants to be single-threaded ("poll() model", not "threads
model") and it wants to communicate with user and examine debuggee symbols and
memory data it cannot use sleeping wait. GDB is single-threaded and it
supports `set target-async 1': info '(gdb)Background Execution'
Thanks,
Jan
next prev parent reply other threads:[~2011-05-15 17:47 UTC|newest]
Thread overview: 115+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-08 15:48 [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification Tejun Heo
2011-05-08 15:48 ` [PATCH 01/11] job control: rename signal->group_stop and flags to jobctl and rearrange flags Tejun Heo
2011-05-08 15:48 ` [PATCH 02/11] ptrace: implement PTRACE_SEIZE Tejun Heo
2011-05-09 16:18 ` Oleg Nesterov
2011-05-10 9:46 ` Tejun Heo
2011-05-10 13:20 ` Oleg Nesterov
2011-05-10 13:47 ` Tejun Heo
2011-05-10 18:19 ` Oleg Nesterov
2011-05-15 15:56 ` PTRACE_SEIZE should not stop [Re: [PATCH 02/11] ptrace: implement PTRACE_SEIZE] Jan Kratochvil
2011-05-15 16:26 ` Tejun Heo
2011-05-15 17:15 ` Jan Kratochvil
2011-05-15 17:25 ` Tejun Heo
2011-05-15 19:48 ` Jan Kratochvil
2011-05-16 8:31 ` Tejun Heo
2011-05-16 12:26 ` Jan Kratochvil
2011-05-16 12:42 ` Tejun Heo
2011-05-16 13:03 ` Jan Kratochvil
2011-05-16 13:51 ` Tejun Heo
2011-05-16 13:21 ` Jan Kratochvil
2011-05-16 13:45 ` Tejun Heo
2011-05-16 13:48 ` Jan Kratochvil
2011-05-16 13:54 ` Tejun Heo
2011-05-08 15:48 ` [PATCH 03/11] ptrace: ptrace_check_attach(): rename @kill to @ignore_state and add comments Tejun Heo
2011-05-08 15:48 ` [PATCH 04/11] ptrace: implement PTRACE_INTERRUPT Tejun Heo
2011-05-08 21:58 ` Denys Vlasenko
2011-05-09 10:09 ` Tejun Heo
2011-05-09 10:55 ` Denys Vlasenko
2011-05-09 16:58 ` Oleg Nesterov
2011-05-10 9:50 ` Tejun Heo
2011-05-10 14:06 ` Oleg Nesterov
2011-05-10 14:20 ` Tejun Heo
2011-05-10 18:08 ` Oleg Nesterov
2011-05-11 8:29 ` Tejun Heo
2011-05-12 17:06 ` Oleg Nesterov
2011-05-12 17:21 ` Tejun Heo
2011-05-10 21:59 ` Denys Vlasenko
2011-05-11 9:19 ` Tejun Heo
2011-05-11 12:23 ` Denys Vlasenko
2011-05-11 13:22 ` Tejun Heo
2011-05-11 16:20 ` Bryan Donlan
2011-05-11 19:24 ` Tejun Heo
2011-05-15 16:10 ` PTRACE_DETACH without stop [Re: [PATCH 04/11] ptrace: implement PTRACE_INTERRUPT] Jan Kratochvil
2011-05-15 16:35 ` Tejun Heo
2011-05-15 17:39 ` Jan Kratochvil
2011-05-16 9:01 ` Tejun Heo
2011-05-16 12:08 ` Jan Kratochvil
2011-05-16 12:24 ` Tejun Heo
2011-05-08 15:48 ` [PATCH 05/11] ptrace: restructure ptrace_getsiginfo() Tejun Heo
2011-05-08 15:49 ` [PATCH 06/11] ptrace: make group stop state visible via PTRACE_GETSIGINFO Tejun Heo
2011-05-10 16:55 ` Oleg Nesterov
2011-05-10 17:11 ` Oleg Nesterov
2011-05-11 8:08 ` Tejun Heo
2011-05-12 16:47 ` Oleg Nesterov
2011-05-12 17:15 ` Tejun Heo
2011-05-08 15:49 ` [PATCH 07/11] ptrace: add JOBCTL_TRAPPED Tejun Heo
2011-05-08 15:49 ` [PATCH 08/11] ptrace: move fallback JOBCTL_TRAPPING clearing to get_signal_to_deliver() Tejun Heo
2011-05-11 15:48 ` Oleg Nesterov
2011-05-11 19:17 ` Tejun Heo
2011-05-12 15:40 ` Oleg Nesterov
2011-05-08 15:49 ` [PATCH 09/11] job control: reorganize wait_task_stopped() Tejun Heo
2011-05-11 15:48 ` Oleg Nesterov
2011-05-11 19:29 ` Tejun Heo
2011-05-12 15:42 ` Oleg Nesterov
2011-05-12 16:02 ` Tejun Heo
2011-05-12 17:25 ` Oleg Nesterov
2011-05-12 17:32 ` Tejun Heo
2011-05-12 17:33 ` Tejun Heo
2011-05-12 18:33 ` Oleg Nesterov
2011-05-13 8:46 ` Tejun Heo
2011-05-13 17:21 ` Oleg Nesterov
2011-05-14 10:56 ` Tejun Heo
2011-05-15 14:40 ` waitpid(WNOHANG) should report SIGCHLD-notified signals [Re: [PATCH 09/11] job control: reorganize wait_task_stopped()] Jan Kratochvil
2011-05-15 16:47 ` Tejun Heo
2011-05-15 17:01 ` Tejun Heo
2011-05-15 17:47 ` Jan Kratochvil [this message]
2011-05-16 9:13 ` Tejun Heo
2011-05-16 12:11 ` Jan Kratochvil
2011-05-16 12:27 ` Tejun Heo
2011-05-16 12:39 ` Jan Kratochvil
2011-05-16 12:46 ` Tejun Heo
2011-05-08 15:49 ` [PATCH 10/11] ptrace: move JOBCTL_TRAPPING wait to wait(2) and ptrace_check_attach() Tejun Heo
2011-05-11 16:49 ` Oleg Nesterov
2011-05-11 17:00 ` Oleg Nesterov
2011-05-11 19:45 ` Tejun Heo
2011-05-11 19:53 ` Tejun Heo
2011-05-12 10:23 ` Tejun Heo
2011-05-12 16:06 ` Oleg Nesterov
2011-05-12 15:59 ` Oleg Nesterov
2011-05-12 16:07 ` Tejun Heo
2011-05-12 18:20 ` Oleg Nesterov
2011-05-13 9:13 ` Tejun Heo
2011-05-13 18:34 ` Oleg Nesterov
2011-05-08 15:49 ` [PATCH 11/11] ptrace: implement group stop notification for ptracer Tejun Heo
2011-05-08 22:42 ` Denys Vlasenko
2011-05-09 10:10 ` Tejun Heo
2011-05-10 22:37 ` Denys Vlasenko
2011-05-11 9:05 ` Tejun Heo
2011-05-11 12:01 ` Denys Vlasenko
2011-05-11 13:13 ` Tejun Heo
2011-05-11 19:58 ` Oleg Nesterov
2011-05-11 20:18 ` Tejun Heo
2011-05-11 20:21 ` Tejun Heo
2011-05-12 10:24 ` Tejun Heo
2011-05-15 14:02 ` getter PTRACE_GETSIGINFO should not modify anything [Re: [PATCH 11/11] ptrace: implement group stop notification for ptracer] Jan Kratochvil
2011-05-15 14:28 ` Tejun Heo
2011-05-15 17:17 ` Jan Kratochvil
2011-05-15 17:28 ` Tejun Heo
2011-05-15 20:06 ` Jan Kratochvil
2011-05-16 8:43 ` Tejun Heo
2011-05-16 12:17 ` Jan Kratochvil
2011-05-16 12:56 ` Tejun Heo
2011-05-16 13:00 ` Ingo Molnar
2011-05-08 22:27 ` [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification Denys Vlasenko
2011-05-09 9:48 ` Tejun Heo
2011-05-15 13:55 ` ptrace-testsuite status [Re: [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification] Jan Kratochvil
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