From: ebiederm@xmission.com (Eric W. Biederman)
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Davide Libenzi <davidel@xmailserver.org>,
Ingo Molnar <mingo@elte.hu>,
Linus Torvalds <torvalds@linux-foundation.org>,
Roland McGrath <roland@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] ptrace_stop: remove the wrong ->group_stop_count bookkeeping
Date: Sat, 08 Dec 2007 17:31:51 -0700 [thread overview]
Message-ID: <m1wsroogi0.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <20071208183801.GA9943@tv-sign.ru> (Oleg Nesterov's message of "Sat, 8 Dec 2007 21:38:01 +0300")
Oleg Nesterov <oleg@tv-sign.ru> writes:
> ptrace_stop() decrements ->group_stop_count to "participate" in group stop.
> This looks very wrong to me, the task can in fact decrement this counter twice.
> If the tracee returns to the user-space before other threads complete the group
> stop, it will notice TIF_SIGPENDING and do it again.
This is one of those interesting weird cases. The ptrace interface remains per
task.
So need to handle a simultaneous thread group stop and a per task stop.
>
> Another problem is that we don't set SIGNAL_STOP_STOPPED if the counter becomes
> zero.
>
> I must admit, I don't undestand the reason why this code was added, it is very
> old.
I haven't dug in enough yet to understand better, but it is my hunch we
need to do something when we have both kinds of stop happening simultaneously.
Eric
next prev parent reply other threads:[~2007-12-09 0:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-08 18:38 [PATCH 2/3] ptrace_stop: remove the wrong ->group_stop_count bookkeeping Oleg Nesterov
2007-12-09 0:31 ` Eric W. Biederman [this message]
2007-12-09 14:05 ` Oleg Nesterov
2008-01-10 10:41 ` Petr Tesarik
2008-01-10 21:39 ` Oleg Nesterov
2008-01-11 8:50 ` Petr Tesarik
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