Re: [Xen-devel] [PATCH] fix event channel notification loss on IA64

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Thu, Jun 29, 2006 at 02:28:37PM +0100, Keir Fraser wrote:
> 
> On 29 Jun 2006, at 06:43, Isaku Yamahata wrote:
> 
> >evtchn_do_upcall() has a micro optimization which is depends on
> >that xchg is a barrier.
> >However xchg of IA64 has acquire semantics so that event
> >channel notification is lost sometimes. This patch fixes it.
> 
> clear_bit() isn't a barrier either (at least according to Linux bitop 
> semantics). You want 'rmb();'. I suggest just putting it inside ifndef 
> CONFIG_X86, with the comment about XCHG being a barrier on x86 placed 
> just before the ifndef. Leave the zap of pending flag as a plain write.

I see. Here is the updated patch.


-- 
yamahata

Attachment: 10521:cc21edd63141_memory_barrier_evtchn_do_upcall.patch
Description: Text document

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