Prev: [PATCH-v2 3/8] cpuidle: make cpuidle_curr_driver static
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From: Jiri Slaby on 27 May 2010 02:20
On 05/26/2010 11:25 PM, Haiyang Zhang wrote:
>> From: Greg KH [mailto:gregkh(a)suse.de]
>>> + VmbusChannelOpen(newChannel, 2 * PAGE_SIZE,
>>> + 2 * PAGE_SIZE, NULL, 0,
>>> + hv_cb_utils[cnt].callback,
>>> + newChannel) == 0) {
>>> + hv_cb_utils[cnt].channel = newChannel;
>>> + mb();
>>
>> What is the mb() call for? Why is it necessary? (hint, if you need it,
>> something else is really wrong...)
>
> It ensures the channel assignment happens before the wakeup call:
> osd_WaitEventSet(ic_channel_ready), if the compiler optimization re-arrange
> the execution order.

wake_up() is a barrier, you don't need the mb() there.

BTW osd_WaitEventSet et al. can be easily converted to completion.

--
js
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Prev: [PATCH-v2 3/8] cpuidle: make cpuidle_curr_driver static
Next: writeback: lessen sync_supers wakeup count