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Date: Mon, 12 Dec 2011 17:57:31 +0800
From: Ming Lei <tom.leiming@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: gregkh@...e.de, akpm@...ux-foundation.org,
linux-kernel@...r.kernel.org, ostrikov@...dia.com,
adobriyan@...il.com, eric.dumazet@...il.com, mingo@...e.hu,
Oliver Neukum <oneukum@...e.de>
Subject: Re: [PATCH 3/3] kref: Remove the memory barriers
On Mon, Dec 12, 2011 at 4:54 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, 2011-12-12 at 11:48 +0800, Ming Lei wrote:
>> For kref, maybe it is still multiple operations done on one cpu vs them
>> being visible on another, but seems a bit implicit, see the common kref
>> usage below:
>>
>> CPU0 CPU1
>> A:kref_init(&obj->ref)
>
> how does CPU0 get a ref to obj?
Suppose open/close/read/.. context is run on CPU0, and driver .probe/.release
context(hotplug context) is run on CPU1. There are a few examples on
usb driver(eg. usb-skeleton.c, ...)
>
>> B:kref_get(&obj->ref)
>> C:access obj E:access obj
>> F:kref_put(&ojb->ref)
>> D:kref_put(obj->ref)
thanks,
--
Ming Lei
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