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Date: Fri, 26 May 2017 06:06:14 -0400 From: Keith Busch <keith.busch@...el.com> To: Rakesh Pandit <rakesh@...era.com> Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me> Subject: Re: [PATCH V2 1/1] nvme: fix multiple ctrl removal scheduling On Wed, May 24, 2017 at 05:26:25PM +0300, Rakesh Pandit wrote: > Commit c5f6ce97c1210 tries to address multiple resets but fails as > work_busy doesn't involve any synchronization and can fail. This is > reproducible easily as can be seen by WARNING below which is triggered > with line: > > WARN_ON(dev->ctrl.state == NVME_CTRL_RESETTING) > > Allowing multiple resets can result in multiple controller removal as > well if different conditions inside nvme_reset_work fail and which > might deadlock on device_release_driver. > > This patch makes sure that work queue item (reset_work) is added only > if controller state != NVME_CTRL_RESETTING and that is achieved by > moving state change outside nvme_reset_work into nvme_reset and > removing old work_busy call. State change is always synchronizated > using controller spinlock. So, the reason the state is changed when the work is running rather than queueing is for the window when the state may be set to NVME_CTRL_DELETING, and we don't want the reset work to proceed in that case. What do you think about adding a new state, like NVME_CTRL_SCHED_RESET, then leaving the NVME_CTRL_RESETTING state change as-is?
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