linux-kernel - [PATCH] scsi_lib.c: sleeping function called from invalid context

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Date:	Wed, 23 Sep 2009 17:58:47 +0000
From:	iceberg <strakh@...ras.ru>
To:	James.Bottomley@...senpartnership.com, eric@...ante.org,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] scsi_lib.c: sleeping function called from invalid context

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.

Signed-off-by: Alexander Strakh <strakh@...ras.ru>

---
diff --git a/./a/drivers/scsi/scsi_lib.c b/./b/drivers/scsi/scsi_lib.c
index f3c4089..a8f8e2f 100644
--- a/./a/drivers/scsi/scsi_lib.c
+++ b/./b/drivers/scsi/scsi_lib.c
@@ -353,9 +353,9 @@ static void scsi_single_lun_run(struct scsi_device 
*current_sdev)
 
 		spin_unlock_irqrestore(shost->host_lock, flags);
 		blk_run_queue(sdev->request_queue);
-		spin_lock_irqsave(shost->host_lock, flags);
 	
-		scsi_device_put(sdev);
+		scsi_device_put(sdev);	
+		spin_lock_irqsave(shost->host_lock, flags);
 	}
  out:
 	spin_unlock_irqrestore(shost->host_lock, flags);

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