On Fri, May 21, 2021 at 03:42:31PM +0900, Sergey Senozhatsky wrote: > On (21/05/20 17:14), Paul E. McKenney wrote: > > > On a side note. > > > > > > I wish we didn't have to put kvm_check_and_clear_guest_paused() all > > > over the place. > > > > > > We do load jiffies at the start of check_cpu_stall(). So, in theory, > > > we can just use that captured jiffies (which can become obsolete but > > > so will grace period timestamps) value and never read current system > > > jiffies because they can jump way forward. IOW > > > > > > jn = j + 3 * rcu_jiffies_till_stall_check() + 3; > > > > > > instead of > > > > > > jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; > > > > > > Then we probably can remove kvm_check_and_clear_guest_paused(). > > > > > > But that "don't load current jiffies" is rather fragile. > > > > > > kvm_check_and_clear_guest_paused() is not pretty, but at least it's > > > explicit. > > > > If this works for you, I am very much in favor! > > Oh, no. Sorry for the noise. This is racy and won't work. I had been hoping! ;-) Thanx, Paul
