Re: [PATCH V7 6/6] SCSI: set block queue at preempt only when SCSI device is put into quiesce
From: Christoph Hellwig <hch@infradead.org>
Date: 2017-10-02 13:52:28
Also in:
linux-scsi, lkml, stable
+ /* + * Simply quiesing SCSI device isn't safe, it is easy + * to use up requests because all these allocated requests + * can't be dispatched when device is put in QIUESCE. + * Then no request can be allocated and we may hang + * somewhere, such as system suspend/resume. + * + * So we set block queue in preempt only first, no new + * normal request can enter queue any more, and all pending + * requests are drained once blk_set_preempt_only() + * returns. Only RQF_PREEMPT is allowed in preempt only mode. + */ + blk_set_preempt_only(sdev->request_queue, true); + mutex_lock(&sdev->state_mutex); err = scsi_device_set_state(sdev, SDEV_QUIESCE);
Why is this not under state_mutex so that we guarantee it's atomic vs sdev state changes?
quoted hunk ↗ jump to hunk
@@ -2964,6 +2981,8 @@ void scsi_device_resume(struct scsi_device *sdev) scsi_device_set_state(sdev, SDEV_RUNNING) == 0) scsi_run_queue(sdev->request_queue); mutex_unlock(&sdev->state_mutex); + + blk_set_preempt_only(sdev->request_queue, false);
Same here.