Date: Wed, 25 Mar 2015 13:08:58 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r280586 - stable/8/sys/kern Message-ID: <201503251308.t2PD8wEm065217@svn.freebsd.org>
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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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