On 06/25/13 19:40, James Bottomley wrote:
If I look at what we actually do: all the HBAs treat scsi_remove_host as a waited for transition. The reason this works is the loop over __scsi_remove_device() in scsi_forget_host(). By the time that loop returns, every scsi_device is gone (and so is every target). Because blk_cleanup_queue() induces a synchronous wait for the queue to die in __scsi_remove_device(), there can be no outstanding I/O and no eh activity for the device when it returns (and no possibility of starting any). Thus at the end of scsi_forget_host, we have no devices to start I/O and no eh activity, so the final put will be the last.
With the patch at the start of this thread everything works like you described above. However, without that patch EH activity can continue after scsi_remove_device() has returned. I have seen that occurring several times while testing SCSI LLD patches.
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