From 2793ea13aaf96684ffa606eaf0856d3cdcce9a00 Mon Sep 17 00:00:00 2001 From: Hans Petter Selasky Date: Sun, 22 Mar 2015 13:11:56 +0000 Subject: [PATCH] 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 --- sys/kern/kern_conf.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c index 79c8fea69e0d..20565420704d 100644 --- a/sys/kern/kern_conf.c +++ b/sys/kern/kern_conf.c @@ -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();