On Thu, 1 Aug 2019, Oleg Nesterov wrote: > On 08/01, Thomas Gleixner wrote: > > > > @@ -8172,6 +8174,10 @@ static int vcpu_run(struct kvm_vcpu *vcp > > ++vcpu->stat.signal_exits; > > break; > > } > > + > > + if (notify_resume_pending()) > > + tracehook_handle_notify_resume(); > > shouldn't you drop kvm->srcu before tracehook_handle_notify_resume() ? > > I don't understand this code at all, but vcpu_run() does this even before > cond_resched(). Yeah, I noticed that it's dropped around cond_resched(). My understanding is that for voluntary giving up the CPU via cond_resched() it needs to be dropped. For involuntary preemption (CONFIG_PREEMPT=y) it's not required as the whole code section after preempt_enable() is fully preemptible. Now the 1Mio$ question is whether any of the notify functions invokes cond_resched() and whether that really matters. Paolo? Thanks, tglx
