scsi_lib.c: avoid calling scsi_device_put() from under ->host_lock

From: Alexander Strakh <[email protected]>

Driver scsi_lib.c might sleep in atomic context, because it calls scsi_device_put under spin_lock_irqsave.

drivers/scsi/scsi_lib.c:356:

	spin_lock_irqsave(shost->host_lock, flags);
	scsi_device_put(sdev);

Path to might_sleep macro from scsi_device_put:
1. scsi_device_put calls put_device at ./drivers/scsi/scsi.c:1111
2. put_device calls kobject_put at ./drivers/base/core.c:1038
3. kobject_put calls kref_put at ./lib/kobject.c
4. kref_put may call callback function kobject_release at ./lib/kref.c if refcount becomes zero, which might_sleep because it calls user event. Details:
4.1 kobject_cleanup calls kobject_uevent at ./lib/kobject.c:555 4.2 kobject_uevent calls kobject_uevent_env at ./lib/kobject_uevent.c:282 4.3 kobject_uevent_env calls call_usermodehelper_exec at
./include/linux/kmod.h:83
4.4 call_usermodehelper_exec calls wait_for_completion at
./kernel/kmod.c:481
4.5 wait_for_completion calls wait_for_common at ./kernel/sched.c:5710 4.5 wait_for_common calls might_sleep at ./kernels/sched.c:5692

Found by Linux Driver Verification project.

Delete wrong sleeping function calls.

---

 drivers/scsi/scsi_lib.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN drivers/scsi/scsi_lib.c~scsi_libc-avoid-calling-scsi_device_put-from-under-host_lock drivers/scsi/scsi_lib.c
@@ -353,9 +353,9 @@ static void scsi_single_lun_run(struct s
 
 		spin_unlock_irqrestore(shost->host_lock, flags);
 		blk_run_queue(sdev->request_queue);
-		spin_lock_irqsave(shost->host_lock, flags);
 	
 		scsi_device_put(sdev);
+		spin_lock_irqsave(shost->host_lock, flags);
 	}
  out:
 	spin_unlock_irqrestore(shost->host_lock, flags);

_

I thought I already gave an explanation why this is the wrong analysis ... sorry on a plane and can't look it up.

James