On Wed, 07 Dec 2011, Avi Kivity wrote: > On 12/05/2011 10:19 PM, Eric B Munson wrote: > > When a host stops or suspends a VM it will set a flag to show this. The > > watchdog will use these functions to determine if a softlockup is real, or > > the > > result of a suspended VM. > > > > +bool kvm_check_and_clear_guest_paused(int cpu) > > +{ > > + bool ret = false; > > + struct pvclock_vcpu_time_info *src; > > + > > + /* > > + * per_cpu() is safe here because this function is only called from > > + * timer functions where preemption is already disabled. > > + */ > > + WARN_ON(!in_atomic()); > > + src = &per_cpu(hv_clock, cpu); > > __get_cpu_var(); drop the cpu argument >
Will change for V6. > > + if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { > > + src->flags = src->flags & (~PVCLOCK_GUEST_STOPPED); > > Isn't this racy? Between reading and writing src->flags, we can exit to > the hypervisor and add/remove new flags. The write then overrides those > new flags. > If I understand (please correct me if this is wrong) because this is only called from the watchdog, which disables preemption, we should be protected from something else writing to these flags. > > + ret = true; > > + } > > + > > + return ret; > > +} > > +EXPORT_SYMBOL_GPL(kvm_check_and_clear_guest_paused); > > + > > static struct clocksource kvm_clock = { > > .name = "kvm-clock", > > .read = kvm_clock_get_cycles, > > > -- > error compiling committee.c: too many arguments to function >
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