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Fix for out of order device destruction notifications when using the

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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
This commit is contained in:
Hans Petter Selasky 2015-03-22 13:11:56 +00:00
parent c66d17c7bc
commit 2793ea13aa
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=280345
1 changed files with 18 additions and 2 deletions
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20
sys/kern/kern_conf.c
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@ -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();