Hi, James, On 2016/12/10 0:02, James Bottomley wrote: > On Fri, 2016-12-09 at 17:35 +0800, Wei Fang wrote: >> A scan work can run simultaneously with fc_remote_port_delete(). >> If a scsi device is added to the ->__devices list in the scan work, >> it can be touched and will be blocked in scsi_target_block(), which >> will be called in fc_remote_port_delete(), and QUEUE_FLAG_STOPPED >> flag will be setted to the scsi device's request queue. >> >> The scsi device is being setted to the SDEV_RUNNING state in >> scsi_sysfs_add_sdev() at the end of the scan work. When the remote >> port reappears, scsi_target_unblock() will be called, but the >> QUEUE_FLAG_STOPPED flag will not be cleared, since >> scsi_internal_device_unblock() ignores SCSI devices in SDEV_RUNNING >> state. It results in a permanent stop of the scsi device's request >> queue. Every requests sended to it will be blocked. > > This is a bit unclear as a description of the problem > >> Since the scsi device shouldn't be unblocked in this case, fix >> it by removing scsi_device_set_state() in scsi_sysfs_add_sdev(). > > So is this as a description of the solution, because the reader doesn't > know there's a prior place where SDEV_RUNNING was previously set. > > How about > > --- > A race between scanning and fc_remote_port_delete() may result in a > permanent stop if the device gets blocked before scsi_sysfs_add_lun() > and unblocked after. The reason is that blocking a device sets both > the SDEV_BLOCKED state and the QUEUE_FLAG_STOPPED. However, > scsi_sysfs_add_sdev() unconditionally sets SDEV_RUNNING which causes > the device to be ignored by scsi_target_unblock() and thus never have > its QUEUE_FLAG_STOPPED cleared leading to a device which is apparently > running but has a stopped queue. > > We actually have two places where SDEV_RUNNING is set: once in > scsi_add_lun() which respects the blocked flag and once in > scsi_sysfs_add_sdev() which doesn't. Since the second set is entirely > spurious, simply remove it to fix the problem.
That's much clearer, thanks. I'll use this in patch v3. Thanks, Wei -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
