On 5/22/19 10:28 PM, Keith Busch wrote: > On Wed, May 22, 2019 at 10:20:45PM +0200, Bart Van Assche wrote: >> On 5/22/19 7:48 PM, Keith Busch wrote: >>> Hardware may temporarily stop processing commands that have >>> been dispatched to it while activating new firmware. Some target >>> implementation's paused state time exceeds the default request expiry, >>> so any request dispatched before the driver could quiesce for the >>> hardware's paused state will time out, and handling this may interrupt >>> the firmware activation. >>> >>> This two-part series provides a way for drivers to reset dispatched >>> requests' timeout deadline, then uses this new mechanism from the nvme >>> driver's fw activation work. >> >> Hi Keith, >> >> Is it essential to modify the block layer to implement this behavior >> change? Would it be possible to implement this behavior change by >> modifying the NVMe driver only, e.g. by modifying the nvme_timeout() >> function and by making that function return BLK_EH_RESET_TIMER while new >> firmware is being activated? > > Good question. > > We can't just do this from nvme_timeout(), though. That introduces races > between timeout_work and fw_act_work if that fw work clears the > condition that timeout needs to observe to return RESET_TIMER. > > Even if we avoid that race, the rq->deadline needs to be adjusted to > the current time after the h/w unpause because the time accumulated while > h/w halted itself should not be counted against the request. Hi Keith, How about recording the time at which the firmware upgrade finished and making nvme_timeout() return RESET_TIMER if either a firmware upgrade is in progress or if it has finished less than (request timeout) seconds ago? The reason I'm asking this is because I'm concerned that the patches you posted would need a careful review to see whether or not these trigger new race conditions. Thanks, Bart.
