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Subject: [patch] lockdep: annotate pktcdvd natural device hierarchy
From: Arjan van de Ven <arjan@linux.intel.com>
To: Peter Osterlund <petero2@telia.com>
Cc: mingo@elte.hu, akpm@osdl.org, Laurent Riffard <laurent.riffard@free.fr>,
       Kernel development list <linux-kernel@vger.kernel.org>, axboe@suse.de
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Date: Sat, 15 Jul 2006 09:04:58 +0200
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> So the claim from the lockdep code, "BUG: possible circular locking
> deadlock detected!", is a false alarm.

ok this patch ought to kill the false positive:


the pkt_*_dev functions operate on not-this-blockdevice, and that is
sufficiently checked at setup time. As a result there is a natural
hierarchy, which needs nesting annotations

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

Index: linux-2.6.18-rc1/drivers/block/pktcdvd.c
===================================================================
--- linux-2.6.18-rc1.orig/drivers/block/pktcdvd.c
+++ linux-2.6.18-rc1/drivers/block/pktcdvd.c
@@ -2577,19 +2577,19 @@ static int pkt_ctl_ioctl(struct inode *i
 	case PKT_CTRL_CMD_SETUP:
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
-		mutex_lock(&ctl_mutex);
+		mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
 		ret = pkt_setup_dev(&ctrl_cmd);
 		mutex_unlock(&ctl_mutex);
 		break;
 	case PKT_CTRL_CMD_TEARDOWN:
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
-		mutex_lock(&ctl_mutex);
+		mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
 		ret = pkt_remove_dev(&ctrl_cmd);
 		mutex_unlock(&ctl_mutex);
 		break;
 	case PKT_CTRL_CMD_STATUS:
-		mutex_lock(&ctl_mutex);
+		mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
 		pkt_get_status(&ctrl_cmd);
 		mutex_unlock(&ctl_mutex);
 		break;