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From: Oleg Nesterov <oleg@redhat.com>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Roland McGrath <roland@hack.frob.com>, Tejun Heo <tj@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: ptrace() hangs on attempt to seize/attach stopped & frozen task
Date: Tue, 10 Nov 2015 21:20:07 +0100	[thread overview]
Message-ID: <20151110201950.GA4925@redhat.com> (raw)
In-Reply-To: <20151109185506.GA22744@redhat.com>

On 11/09, Oleg Nesterov wrote:
>
> Hi,
>
> On 11/09, Andrey Ryabinin wrote:
> >
> > Hi,
> >
> > So, the ptrace() hangs if we try to attach to stopped task from freezing cgroup.
> > It seems this was introduced by 5d8f72b55c2756("freezer: change ptrace_stop/do_signal_stop to use freezable_schedule()").
>
> quite possible...

Not really, this was broken before that commit. Note that try_to_freeze()
was called under "relock:" label, so we had the same problem: the tracee
doesn't do do_jobctl_trap() after do_signal_stop() without try_to_freeze()
in between. Not that it matters, but still.

Oleg.


  parent reply	other threads:[~2015-11-10 19:24 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-09 15:12 ptrace() hangs on attempt to seize/attach stopped & frozen task Andrey Ryabinin
2015-11-09 18:55 ` Oleg Nesterov
2015-11-09 18:02   ` Tejun Heo
2015-11-10 20:20     ` Oleg Nesterov
2015-11-16 18:45       ` Tejun Heo
2015-11-17 19:34         ` Oleg Nesterov
2015-11-17 18:57           ` Tejun Heo
2015-11-19 16:49           ` Pedro Alves
2015-11-19 17:47             ` Oleg Nesterov
2015-11-19 18:08               ` Pedro Alves
2015-11-10 20:20   ` Oleg Nesterov [this message]
2015-11-19 18:47 ` [PATCH 0/2] (Was: ptrace() hangs on attempt to seize/attach stopped & frozen task) Oleg Nesterov
2015-11-19 18:47   ` [PATCH 1/2] ptrace: make wait_on_bit(JOBCTL_TRAPPING_BIT) in ptrace_attach() killable Oleg Nesterov
2015-11-23 23:05     ` Tejun Heo
2015-11-19 18:47   ` [PATCH 2/2] ptrace: task_stopped_code(ptrace => true) can't see TASK_STOPPED task Oleg Nesterov
2015-11-23 23:15     ` Tejun Heo

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