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RE: [Xen-devel] [PATCH] Yield to VCPU hcall, spinlock yielding

To: "Orran Y Krieger" <okrieg@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Yield to VCPU hcall, spinlock yielding
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Tue, 7 Jun 2005 11:38:14 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Bryan S Rosenburg <rosnbrg@xxxxxxxxxx>, hohnbaum@xxxxxxxxxx, ryanh@xxxxxxxxxx, xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
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Thread-index: AcVqmb1+dqanAoPjR32Ghb2KQZOsdgAsp1Tg
Thread-topic: [Xen-devel] [PATCH] Yield to VCPU hcall, spinlock yielding
> You can only use spinlock accounting for dealing with locking 
> issues in kernel (unless you are willing to change 
> application level programs and libs).  If preemption 
> notification overhead is not prohibitive, the fact that it 
> solves the application problem as well as the kernel problem 
> seems like a compelling advantage over spinlock accounting, 
> doesn't it? 


Are you assuming the pre-emption notification is going to get propagated
to user-space as a signal, and that user space applications would be
modified to take advantage of the signal? (possibly this could be hidden
in the pthread library?} Since the kernel doesn't know when user space
has an application lock or not, that's going to be a lot of signals. 


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