Subject: Re: [Lse-tech] Re: [Patch 4/7] Add sysctl for delay accounting
From: Arjan van de Ven <arjan@infradead.org>
To: balbir@in.ibm.com
Cc: dipankar@in.ibm.com, Shailabh Nagar <nagar@watson.ibm.com>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       lse-tech <lse-tech@lists.sourceforge.net>
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Date: Mon, 27 Feb 2006 12:24:18 +0100
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> 
> One of the reasons that alloc_delays() is a bit ugly is to handle the case
> that tasks might get created between the two loops. Even with RCU kind of
> locking (except for changing the locking primitives of-course), this code would
> work fine. Once delayacct_on is set to 1, copy_process() should take care of
> allocating the delays structure. alloc_delays() re-iterates through the list
> of tasks to find tasks whose allocation got missed. This revisit happens
> at most once due to the small window in which we check for delayacct_on
> and allocate the task's delays structure. If tasks are missed within that
> window, we revisit the tasks again and allocate for them.

well you assume you CAN walk all tasks... which is something afaik
that's being deprecated ;)


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