Since scsi_target_unblock() uses starget_for_each_device(), since
starget_for_each_device() uses scsi_device_get(), since
scsi_device_get() fails after unloading of the LLD kernel module
has been started scsi_target_unblock() may skip devices that were
affected by scsi_target_block(). Ensure that scsi_target_block()
examines all SCSI devices. This patch avoids that unloading the
ib_srp kernel module can trigger the following hang:
Call Trace:
schedule+0x35/0x80
schedule_timeout+0x237/0x2d0
io_schedule_timeout+0xa6/0x110
wait_for_completion_io+0xa3/0x110
blk_execute_rq+0xdf/0x120
scsi_execute+0xce/0x150 [scsi_mod]
scsi_execute_req_flags+0x8f/0xf0 [scsi_mod]
sd_sync_cache+0xa9/0x190 [sd_mod]
sd_shutdown+0x6a/0x100 [sd_mod]
sd_remove+0x64/0xc0 [sd_mod]
__device_release_driver+0x8d/0x120
device_release_driver+0x1e/0x30
bus_remove_device+0xf9/0x170
device_del+0x127/0x240
__scsi_remove_device+0xc1/0xd0 [scsi_mod]
scsi_forget_host+0x57/0x60 [scsi_mod]
scsi_remove_host+0x72/0x110 [scsi_mod]
srp_remove_work+0x8b/0x200 [ib_srp]
Reported-by: Israel Rukshin <israelr@xxxxxxxxxxxx>
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Tested-by: Israel Rukshin <israelr@xxxxxxxxxxxx>
Cc: Max Gurtovoy <maxg@xxxxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 19125d72f322..f03a7867c04f 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -3071,21 +3071,37 @@ device_unblock(struct scsi_device *sdev, void *data)
scsi_internal_device_unblock(sdev, *(enum scsi_device_state *)data);
}
+/**
+ * target_unblock() - unblock all devices associated with a SCSI target
+ *
+ * Notes:
+ * - Do not use scsi_device_get() nor any of the macros that use this
+ * function from inside scsi_target_block() because otherwise this function
+ * won't have any effect when called while the SCSI LLD is being unloaded.
+ * - Do not hold the host lock around the device_unblock() calls because at
+ * least for blk-sq the block layer queue lock is the outer lock and the
+ * SCSI host lock is the inner lock.
+ */
static int
target_unblock(struct device *dev, void *data)
{
if (scsi_is_target_device(dev))
- starget_for_each_device(to_scsi_target(dev), data,
+ starget_for_all_devices(to_scsi_target(dev), data,
device_unblock);
return 0;
}
+/**
+ * scsi_target_unblock() - unblock all devices associated with a SCSI target
+ * @dev: Either a pointer to the dev member of struct scsi_target or a pointer
+ * to the shost_gendev member of struct Scsi_Host.
+ * @new_state: New SCSI device state.
+ */
void
scsi_target_unblock(struct device *dev, enum scsi_device_state new_state)
{
if (scsi_is_target_device(dev))
- starget_for_each_device(to_scsi_target(dev), &new_state,
- device_unblock);
+ target_unblock(dev, &new_state);
else
device_for_each_child(dev, &new_state, target_unblock);
}
--
2.12.0
