Re: [PATCH v2] Fix scheduler crash after s3 resume

[Tomasz Wroblewski <tomasz.wroblewski@citrix.com>]

> I think I had already raised the question of the placement of
> this rcu_barrier() here, and the lack of a counterpart in the
> suspend portion of the path. Keir? Or should
> rcu_barrier_action() avoid calling process_pending_softirqs()
> while still resuming, and instead call __do_softirq() with all but
> RCU_SOFTIRQ masked (perhaps through a suitable wrapper,
> or alternatively by open-coding its effect)?
>
>    
Though I recall these vcpu_wake crashes happen also from other entry 
points in enter_state but rcu_barrier, so I dont think removing that 
helps much. Just was unable to get a proper log of them today due to 
most of them being cut in half. Will try bit more.

My belief is that as long as vcpu_migrate is not called in 
cpu_disable_scheduler, the vcpu->processor shall continue to point to 
offline cpu. Which will crash if the vcpu_wake is called for that vcpu. 
If vcpu_migrate is called, then vcpu_wake will still be called with some 
frequency but since vcpu->processor shall point to online cpu, and it 
won't crash. So likely avoiding the wakes here completely is not the 
goal, just the offline ones.