From: Oleg Nesterov <oleg@redhat.com>
To: Roland McGrath <roland@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
Ananth Mavinakayanahalli <ananth@in.ibm.com>,
Christoph Hellwig <hch@infradead.org>,
"Frank Ch. Eigler" <fche@redhat.com>, Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org, utrace-devel@redhat.com
Subject: Re: [RFC,PATCH 14/14] utrace core
Date: Mon, 14 Dec 2009 21:24:54 +0100 [thread overview]
Message-ID: <20091214202454.GA16124@redhat.com> (raw)
In-Reply-To: <20091214194441.4D6BFE24E@magilla.sf.frob.com>
On 12/14, Roland McGrath wrote:
>
> > > In the stopped cases, there are lots of locks and barriers and things
> > > after resuming. (Oleg?)
> >
> > Every time the tracee resumes after TASK_TRACED it uses utrace->lock
> > to synchronize with utrace_control/etc, it must see any changes.
>
> And TASK_STOPPED?
SIGCONT can wake up the TASK_STOPPED tracee. I don't think the tracer
should ever rely on TASK_STOPPED (utrace never does). If the tracer
needs the "really stopped" tracee we have UTRACE_STOP, and this means
TASK_TRACED.
But I am not sure I understand this part of discussion... In any case
the tracee should see any changes which were done before the wakeup.
But TASK_STOPPED can't guarantee the tracee won't be resumed until
the tracer wakes it up. Of course, TASK_TRACED can't prevent SIGKILL,
but in this case we should only care about "the tracee can't resume
until we drop utrace->lock" case.
Oleg.
next prev parent reply other threads:[~2009-12-14 20:30 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-24 20:02 Oleg Nesterov
2009-11-24 20:32 ` Andi Kleen
2009-11-24 20:41 ` Oleg Nesterov
2009-11-24 21:26 ` Andi Kleen
2009-11-24 21:31 ` Frank Ch. Eigler
2009-11-24 21:34 ` Andi Kleen
2009-11-24 21:44 ` Oleg Nesterov
2009-11-25 8:46 ` Andi Kleen
2009-11-25 14:55 ` Oleg Nesterov
2009-11-25 16:00 ` Ingo Molnar
2009-11-25 21:50 ` Christoph Hellwig
2009-12-01 23:47 ` Roland McGrath
2009-12-01 19:54 ` Peter Zijlstra
2009-12-01 22:08 ` Oleg Nesterov
2009-12-07 18:34 ` Peter Zijlstra
2009-12-08 15:04 ` Oleg Nesterov
2009-12-08 15:29 ` Peter Zijlstra
2009-12-08 16:31 ` Oleg Nesterov
2009-12-08 18:19 ` Peter Zijlstra
2009-12-08 18:37 ` Oleg Nesterov
2009-12-13 20:48 ` Roland McGrath
2009-12-08 15:35 ` Peter Zijlstra
2009-12-08 17:51 ` Oleg Nesterov
2009-12-02 5:44 ` Roland McGrath
2009-12-02 18:34 ` Oleg Nesterov
2009-12-02 18:49 ` Oleg Nesterov
2009-12-05 19:14 ` Roland McGrath
2009-12-14 0:25 ` Roland McGrath
2009-12-14 13:51 ` Peter Zijlstra
2009-12-14 17:41 ` Oleg Nesterov
2009-12-14 19:31 ` Oleg Nesterov
2009-12-14 19:42 ` Roland McGrath
2009-12-16 11:18 ` Roland McGrath
2009-12-14 17:03 ` Oleg Nesterov
2009-12-14 19:44 ` Roland McGrath
2009-12-14 20:24 ` Oleg Nesterov [this message]
2009-12-15 2:59 ` Roland McGrath
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