Messages in this thread | | | Date | Thu, 27 May 2010 08:16:55 +0200 | From | Jiri Slaby <> | Subject | Re: [PATCH 1/1] staging: hv: Fix race condition on IC channel initialization (modified) |
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On 05/26/2010 11:25 PM, Haiyang Zhang wrote: >> From: Greg KH [mailto:gregkh@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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