Author: hselasky
Date: Wed Mar 25 13:08:57 2015
New Revision: 280586
URL: https://svnweb.freebsd.org/changeset/base/280586
Log:
MFC r280345:
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()
Modified:
stable/8/sys/kern/kern_conf.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/kern/ (props changed)
Modified: stable/8/sys/kern/kern_conf.c
==============================================================================
--- stable/8/sys/kern/kern_conf.c Wed Mar 25 13:06:37 2015
(r280585)
+++ stable/8/sys/kern/kern_conf.c Wed Mar 25 13:08:57 2015
(r280586)
@@ -929,9 +929,12 @@ 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);
}
@@ -977,12 +980,25 @@ 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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