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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 18 May 2011 22:36:58 +0000 (UTC)
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Subject: svn commit: r222086 - head/sys/kern
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Author: kib
Date: Wed May 18 22:36:58 2011
New Revision: 222086
URL: http://svn.freebsd.org/changeset/base/222086

Log:
  The CDP_ACTIVE flag is cleared at the beginning of destroy_devl(),
  and destroy_devl() drops dev_mtx. The protection against the race
  with dev_rel(), introduced in r163328, should be extended to cover
  destroy_devl() calls for the children of the destroyed dev.
  
  Reported and tested by:	joerg
  MFC after:	1 week

Modified:
  head/sys/kern/kern_conf.c

Modified: head/sys/kern/kern_conf.c
==============================================================================
--- head/sys/kern/kern_conf.c	Wed May 18 22:09:04 2011	(r222085)
+++ head/sys/kern/kern_conf.c	Wed May 18 22:36:58 2011	(r222086)
@@ -981,6 +981,8 @@ destroy_devl(struct cdev *dev)
 	/* Remove name marking */
 	dev->si_flags &= ~SI_NAMED;
 
+	dev->si_refcount++;	/* Avoid race with dev_rel() */
+
 	/* If we are a child, remove us from the parents list */
 	if (dev->si_flags & SI_CHILD) {
 		LIST_REMOVE(dev, si_siblings);
@@ -997,7 +999,6 @@ destroy_devl(struct cdev *dev)
 		dev->si_flags &= ~SI_CLONELIST;
 	}
 
-	dev->si_refcount++;	/* Avoid race with dev_rel() */
 	csw = dev->si_devsw;
 	dev->si_devsw = NULL;	/* already NULL for SI_ALIAS */
 	while (csw != NULL && csw->d_purge != NULL && dev->si_threadcount) {