On Wed, 2018-09-19 at 12:05 +-0800, Ming Lei wrote: +AD4 Looks this patch may introduce the following race between queue +AD4 freeze and +AD4 runtime suspend: +AD4 +AD4 ------------------------------------------------------------------- +AD4 ------- +AD4 CPU0 CPU1 +AD4 CPU2 +AD4 ------------------------------------------------------------------- +AD4 ------- +AD4 +AD4 blk+AF8-freeze+AF8-queue() +AD4 +AD4 blk+AF8-mq+AF8-alloc+AF8-request() +AD4 blk+AF8-queue+AF8-enter() +AD4 blk+AF8-pm+AF8-request+AF8 +AD4 resume() +AD4 wait+AF8-event() +AD4 +AD4 +AD4 blk+AF8-pre+AF8-runtime+AF8-suspend() +AD4 +AD4 -+AD4-blk+AF8-set+AF8-pm+AF8-only +AD4 +AD4 ... +AD4 +AD4 blk+AF8-post+AF8-runtime+AF8-suspend() +AD4 +AD4 ... +AD4 blk+AF8-mq+AF8-unfreeze+AF8-queue() +AD4 ------------------------------------------------------------------- +AD4 ------- +AD4 - CPU0: queue is frozen +AD4 +AD4 - CPU1: one new request comes, and see queue is frozen, but queue +AD4 isn't +AD4 runtime-suspended yet, then blk+AF8-pm+AF8-request+AF8-resume() does nothing. So +AD4 this +AD4 allocation is blocked in wait+AF8-event(). +AD4 +AD4 - CPU2: runtime suspend comes, and queue becomes runtime-suspended +AD4 now +AD4 +AD4 - CPU0: queue is unfreeze, but the new request allocation in CPU1 may +AD4 never +AD4 be done because the queue is runtime suspended, and wait+AF8-event() +AD4 won't return. +AD4 And the expected result is that the queue becomes active and the +AD4 allocation on +AD4 CPU1 is done immediately. Hello Ming, Just like for the scenario Jianchao reported, I will address this by only allowing the suspend to proceed if q+AF8-usage+AF8-counter +AD0APQ 0. Bart.
