From: Oleg Nesterov <oleg@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Roland McGrath <roland@hack.frob.com>, Tejun Heo <tj@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Pedro Alves <palves@redhat.com>,
Jan Kratochvil <jan.kratochvil@redhat.com>
Subject: [PATCH 0/2] (Was: ptrace() hangs on attempt to seize/attach stopped & frozen task)
Date: Thu, 19 Nov 2015 19:47:09 +0100 [thread overview]
Message-ID: <20151119184709.GA19061@redhat.com> (raw)
In-Reply-To: <5640B7F2.70406@virtuozzo.com>
On 11/09, Andrey Ryabinin wrote:
>
> So, the ptrace() hangs if we try to attach to stopped task from freezing cgroup.
OK, lets make it killable at least, TASK_KILLABLE looks better in
any case.
I am starting to think again that we should remove JOBCTL_TRAPPING,
but this needs a bit more discussion and probably testing.
Anyway I agree with Tejun, the freezer doesn't look nice too.
Hmm. I need to re-check but it seems we have another problem...
ptrace_stop() does task_participate_group_stop() and this (in particular)
clears JOBCTL_STOP_PENDING. This is only correct if the task is still traced,
but this is not necessarily true and we can in fact clear JOBCTL_STOP_PENDING
set by __ptrace_unlink() called by the exiting tracer.
Oleg.
next prev parent reply other threads:[~2015-11-19 18:46 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
2015-11-19 18:47 ` Oleg Nesterov [this message]
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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