Re: SMP lockup in virtualized environment

From: Chris Snook
Date: Tue Apr 24 2007 - 18:38:20 EST

LAPLACE Cyprien wrote:
An example: in kernel/pid.c:alloc_pid(), if one of the guest CPUs is
descheduled when holding the pidmap_lock, what happens to the other
guest CPUs who want to alloc/free pids ? Are they blocked too ?

Yup. This is where it's really nice to have directed yields, where you tell the hypervisor to give your physical CPU time to the vcpu that's holding the lock you're blocking on. I know s390 can do this. Perhaps it's something worth generalizing in paravirt_ops?

-- Chris
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