linux-kernel - Re: [PATCH -mm 2/2] ptrace_untrace: fix the SIGNAL_STOP

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Message-Id: <20090220034928.741F6FC2F7@magilla.sf.frob.com>
Date:	Thu, 19 Feb 2009 19:49:28 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm 2/2] ptrace_untrace: fix the SIGNAL_STOP_STOPPED check

> This bug is ancient too. ptrace_untrace() must not resume the task
> if the group stop in progress, we should set TASK_STOPPED instead.

Right, the change looks correct.

> Unfortunately, we still have problems here:
> 
> 	- if the process/thread was traced, SIGNAL_STOP_STOPPED
> 	  does not necessary means this thread group is stopped.
> 
> 	- ptrace breaks the bookkeeping of ->group_stop_count.

Neither of these should be true today as I understand the code.  So if you
have reason to think these, I must be missing something that is likely to
be relevant to reviewing this change.


Thanks,
Roland
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