Re: [PATCH 2/3] block, scsi: Rework runtime power management

On Thu, 2018-07-19 at 06:45 +0800, Ming Lei wrote:

So once blk_freeze_queue_start() returns, percpu_ref�

AF8-is_zero() won't

return true only until the rcu confirmation is done. That means this
approach may not put device down.

Hello Ming,

I agree with your conclusion that it is not guaranteed that q->q_us=
age_counter
is in atomic mode when percpu_ref_is_zero() is called. However,=
 I think that's
fine: if blk_pre_runtime_suspend() returns -EBUSY then the runt=
ime core will
try again at a later time to perform runtime suspend.

Bart.=