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Message-Id: <20091214194441.4D6BFE24E@magilla.sf.frob.com>
Date: Mon, 14 Dec 2009 11:44:41 -0800 (PST)
From: Roland McGrath <roland@...hat.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
Alexey Dobriyan <adobriyan@...il.com>,
Ananth Mavinakayanahalli <ananth@...ibm.com>,
Christoph Hellwig <hch@...radead.org>,
"Frank Ch. Eigler" <fche@...hat.com>, Ingo Molnar <mingo@...e.hu>,
linux-kernel@...r.kernel.org, utrace-devel@...hat.com
Subject: Re: [RFC,PATCH 14/14] utrace core
> Yes, I think this is correct. It is fine to miss ->pending_attach == T,
> and in any case the new attacher can come right after the check, even
> if it was checked under utrace->lock.
Right.
> It is important that the tracee can't miss, say, UTRACE_REPORT request
> (as you already explained), and every time the tracee clears ->resume
> it calls splice_attaching().
Right.
> > 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?
Please send me patches to add whatever comments would make all this clear
enough to Peter when reading the code.
Thanks,
Roland
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