linux-kernel - Re: [PATCH 1/3] sched: fix TASK

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Message-ID: <20080628123825.GA1682@tv-sign.ru>
Date:	Sat, 28 Jun 2008 16:38:25 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Roland McGrath <roland@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Wilcox <matthew@....cx>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] sched: fix TASK_WAKEKILL vs SIGKILL race

On 06/09, Roland McGrath wrote:
>
   ^^^^^
Oops, something is wrong! I received this message today, 06/28.

> > Note this "__TASK_STOPPED | __TASK_TRACED" check in signal_pending_state().
> > This is needed to preserve the current behaviour (ptrace_notify). I hope
> > this check will be removed soon, but this (afaics good) change needs the
> > separate discussion.
> 
> Agreed.  I think it might actually already be safe to drop it, but we can
> get to that after this settles.

Great! I'll re-send the patch which drops it in a minute.

Could you also look at other patches?

	[PATCH 2/3] ptrace: never sleep in TASK_TRACED if SIGKILL'ed
	http://marc.info/?l=linux-kernel&m=121362601402886

	[PATCH 3/3] ptrace: kill may_ptrace_stop()
	http://marc.info/?l=linux-kernel&m=121362601702897

I think ptrace_stop() really needs changes. But I don't know what is
the supposed behaviour of PT_TRACE_EXIT. Should we sleep even if the
task was killed? Should we sleep if the thread was killed because another
one does exit_group() or exec() ?

We can use "SIGNAL_GROUP_EXIT && (group_exit_code & 0x7f)" instead
of signal_group_exit() to be sure that task was killed by the fatal
signal.

Oleg.

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