svn commit: r280345 - head/sys/kern

Hans Petter Selasky hselasky at FreeBSD.org
Sun Mar 22 13:11:58 UTC 2015


Author: hselasky
Date: Sun Mar 22 13:11:56 2015
New Revision: 280345
URL: https://svnweb.freebsd.org/changeset/base/280345

Log:
  Fix for out of order device destruction notifications when using the
  delist_dev() function. In addition to this change:
  - add a proper description of this function
  - add a proper witness assert inside this function
  - switch a nearby line to use the "cdp" pointer instead of cdev2priv()
  
  MFC after:	3 days

Modified:
  head/sys/kern/kern_conf.c

Modified: head/sys/kern/kern_conf.c
==============================================================================
--- head/sys/kern/kern_conf.c	Sun Mar 22 12:49:57 2015	(r280344)
+++ head/sys/kern/kern_conf.c	Sun Mar 22 13:11:56 2015	(r280345)
@@ -1093,9 +1093,12 @@ destroy_devl(struct cdev *dev)
 	}
 
 	dev_unlock();
-	notify_destroy(dev);
+	if ((cdp->cdp_flags & CDP_UNREF_DTR) == 0) {
+		/* avoid out of order notify events */
+		notify_destroy(dev);
+	}
 	mtx_lock(&cdevpriv_mtx);
-	while ((p = LIST_FIRST(&cdev2priv(dev)->cdp_fdpriv)) != NULL) {
+	while ((p = LIST_FIRST(&cdp->cdp_fdpriv)) != NULL) {
 		devfs_destroy_cdevpriv(p);
 		mtx_lock(&cdevpriv_mtx);
 	}
@@ -1141,12 +1144,25 @@ delist_dev_locked(struct cdev *dev)
 	devfs_destroy(dev);
 	LIST_FOREACH(child, &dev->si_children, si_siblings)
 		delist_dev_locked(child);
+	dev_unlock();	
+	/* ensure the destroy event is queued in order */
+	notify_destroy(dev);
+	dev_lock();
 }
 
+/*
+ * This function will delist a character device and its children from
+ * the directory listing and create a destroy event without waiting
+ * for all character device references to go away. At some later point
+ * destroy_dev() must be called to complete the character device
+ * destruction. After calling this function the character device name
+ * can instantly be re-used.
+ */
 void
 delist_dev(struct cdev *dev)
 {
 
+	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "delist_dev");
 	dev_lock();
 	delist_dev_locked(dev);
 	dev_unlock();


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