On Wed, 2018-08-08 at 16:50 +-0800, Ming Lei wrote: +AD4- On Tue, Aug 07, 2018 at 03:51:30PM -0700, Bart Van Assche wrote: +AD4- +AD4- Instead of allowing requests that are not power management requests +AD4- +AD4- to enter the queue in runtime suspended status (RPM+AF8-SUSPENDED), make +AD4- +AD4- the blk+AF8-get+AF8-request() caller block. This change fixes a starvation +AD4- +AD4- Looks not see the related change which blocks blk+AF8-get+AF8-request() in +AD4- this patchset. I was referring to setting pm-only mode for suspended devices. Since blk+AF8-queue+AF8-enter() is called before a request is allocated that is sufficient to make request allocation block. +AD4- +AD4- diff --git a/block/blk-pm.c b/block/blk-pm.c +AD4- +AD4- index bf8532da952d..d6b65cef9764 100644 +AD4- +AD4- --- a/block/blk-pm.c +AD4- +AD4- +-+-+- b/block/blk-pm.c +AD4- +AD4- +AEAAQA- -86,14 +-86,39 +AEAAQA- int blk+AF8-pre+AF8-runtime+AF8-suspend(struct request+AF8-queue +ACo-q) +AD4- +AD4- if (+ACE-q-+AD4-dev) +AD4- +AD4- return ret+ADs- +AD4- +AD4- +AD4- +AD4- +- WARN+AF8-ON+AF8-ONCE(q-+AD4-rpm+AF8-status +ACEAPQ- RPM+AF8-ACTIVE)+ADs- +AD4- +AD4- +- +AD4- +AD4- +- blk+AF8-set+AF8-pm+AF8-only(q)+ADs- +AD4- +AD4- +- /+ACo- +AD4- +AD4- +- +ACo- This function only gets called if the most recent +AD4- +AD4- +- +ACo- pm+AF8-request+AF8-resume() call occurred at least autosuspend+AF8-delay+AF8-ms +AD4- +AD4- +- +ACo- ago. Since blk+AF8-queue+AF8-enter() is called by the request allocation +AD4- +AD4- +- +ACo- code before pm+AF8-request+AF8-resume(), if q+AF8-usage+AF8-counter indicates that +AD4- +AD4- +- +ACo- no requests are in flight it is safe to suspend the device. +AD4- +AD4- +- +ACo-/ +AD4- +AD4- +- ret +AD0- -EBUSY+ADs- +AD4- +AD4- +- if (+ACE-percpu+AF8-ref+AF8-is+AF8-in+AF8-use(+ACY-q-+AD4-q+AF8-usage+AF8-counter)) +AHs- +AD4- +AD4- +- /+ACo- +AD4- +AD4- +- +ACo- Switch to preempt-only mode before calling +AD4- +AD4- +- +ACo- synchronize+AF8-rcu() such that later blk+AF8-queue+AF8-enter() calls +AD4- +AD4- +- +ACo- see the preempt-only state. See also +AD4- +AD4- +- +ACo- http://lwn.net/Articles/573497/. +AD4- +AD4- +- +ACo-/ +AD4- +AD4- +- synchronize+AF8-rcu()+ADs- +AD4- +AD4- +- if (+ACE-percpu+AF8-ref+AF8-is+AF8-in+AF8-use(+ACY-q-+AD4-q+AF8-usage+AF8-counter)) +AD4- +AD4- +- ret +AD0- 0+ADs- +AD4- +AD4- +- +AH0- +AD4- +AD4- +- +AD4- +AD4- In blk+AF8-queue+AF8-enter(), V5 starts to allow all RQF+AF8-PREEMPT requests +AD4- to enter queue even though pm+AF8-only is set. That means any scsi+AF8-execute() +AD4- may issue a new command to host just after the above percpu+AF8-ref+AF8-is+AF8-in+AF8-use() +AD4- returns 0, meantime the suspend is in-progress. +AD4- +AD4- This case is illegal given RQF+AF8-PM is the only kind of request which can be +AD4- issued to hardware during suspend. Right, that's something that needs to be addressed. Bart.
