From owner-svn-src-all@FreeBSD.ORG Mon Jan 19 17:36:53 2015 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id C7F56403; Mon, 19 Jan 2015 17:36:53 +0000 (UTC) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:1900:2254:2068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id B4377D79; Mon, 19 Jan 2015 17:36:53 +0000 (UTC) Received: from svn.freebsd.org ([127.0.1.70]) by svn.freebsd.org (8.14.9/8.14.9) with ESMTP id t0JHar0Q044491; Mon, 19 Jan 2015 17:36:53 GMT (envelope-from kib@FreeBSD.org) Received: (from kib@localhost) by svn.freebsd.org (8.14.9/8.14.9/Submit) id t0JHarYf044488; Mon, 19 Jan 2015 17:36:53 GMT (envelope-from kib@FreeBSD.org) Message-Id: <201501191736.t0JHarYf044488@svn.freebsd.org> X-Authentication-Warning: svn.freebsd.org: kib set sender to kib@FreeBSD.org using -f From: Konstantin Belousov Date: Mon, 19 Jan 2015 17:36:53 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r277391 - in head/sys: fs/devfs kern X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 19 Jan 2015 17:36:54 -0000 Author: kib Date: Mon Jan 19 17:36:52 2015 New Revision: 277391 URL: https://svnweb.freebsd.org/changeset/base/277391 Log: Stop enforcing additional reference on all cdevs, which was introduced in r277199. Acquire the neccessary reference in delist_dev_locked() and inform destroy_devl() about it using CDP_UNREF_DTR flag. Fix some style nits, add asserts. Discussed with: hselasky Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 1 week Modified: head/sys/fs/devfs/devfs_devs.c head/sys/fs/devfs/devfs_int.h head/sys/kern/kern_conf.c Modified: head/sys/fs/devfs/devfs_devs.c ============================================================================== --- head/sys/fs/devfs/devfs_devs.c Mon Jan 19 17:24:52 2015 (r277390) +++ head/sys/fs/devfs/devfs_devs.c Mon Jan 19 17:36:52 2015 (r277391) @@ -137,12 +137,6 @@ devfs_alloc(int flags) vfs_timestamp(&ts); cdev->si_atime = cdev->si_mtime = cdev->si_ctime = ts; cdev->si_cred = NULL; - /* - * Avoid race with dev_rel() by setting the initial - * reference count to 1. This last reference is taken - * by the destroy_dev() function. - */ - cdev->si_refcount = 1; return (cdev); } Modified: head/sys/fs/devfs/devfs_int.h ============================================================================== --- head/sys/fs/devfs/devfs_int.h Mon Jan 19 17:24:52 2015 (r277390) +++ head/sys/fs/devfs/devfs_int.h Mon Jan 19 17:36:52 2015 (r277391) @@ -56,6 +56,7 @@ struct cdev_priv { u_int cdp_flags; #define CDP_ACTIVE (1 << 0) #define CDP_SCHED_DTR (1 << 1) +#define CDP_UNREF_DTR (1 << 2) u_int cdp_inuse; u_int cdp_maxdirent; Modified: head/sys/kern/kern_conf.c ============================================================================== --- head/sys/kern/kern_conf.c Mon Jan 19 17:24:52 2015 (r277390) +++ head/sys/kern/kern_conf.c Mon Jan 19 17:36:52 2015 (r277391) @@ -116,6 +116,8 @@ dev_free_devlocked(struct cdev *cdev) mtx_assert(&devmtx, MA_OWNED); cdp = cdev2priv(cdev); + KASSERT((cdp->cdp_flags & CDP_UNREF_DTR) == 0, + ("destroy_dev() was not called after delist_dev(%p)", cdev)); TAILQ_INSERT_HEAD(&cdevp_free_list, cdp, cdp_list); } @@ -1035,6 +1037,7 @@ destroy_devl(struct cdev *dev) { struct cdevsw *csw; struct cdev_privdata *p; + struct cdev_priv *cdp; mtx_assert(&devmtx, MA_OWNED); KASSERT(dev->si_flags & SI_NAMED, @@ -1043,7 +1046,18 @@ destroy_devl(struct cdev *dev) ("WARNING: Driver mistake: destroy_dev on eternal %d\n", dev2unit(dev))); - devfs_destroy(dev); + cdp = cdev2priv(dev); + if ((cdp->cdp_flags & CDP_UNREF_DTR) == 0) { + /* + * Avoid race with dev_rel(), e.g. from the populate + * loop. If CDP_UNREF_DTR flag is set, the reference + * to be dropped at the end of destroy_devl() was + * already taken by delist_dev_locked(). + */ + dev_refl(dev); + + devfs_destroy(dev); + } /* Remove name marking */ dev->si_flags &= ~SI_NAMED; @@ -1103,19 +1117,27 @@ destroy_devl(struct cdev *dev) } } dev->si_flags &= ~SI_ALIAS; - dev->si_refcount--; /* Avoid race with dev_rel() */ + cdp->cdp_flags &= ~CDP_UNREF_DTR; + dev->si_refcount--; - if (dev->si_refcount > 0) { + if (dev->si_refcount > 0) LIST_INSERT_HEAD(&dead_cdevsw.d_devs, dev, si_list); - } else { + else dev_free_devlocked(dev); - } } static void delist_dev_locked(struct cdev *dev) { + struct cdev_priv *cdp; struct cdev *child; + + mtx_assert(&devmtx, MA_OWNED); + cdp = cdev2priv(dev); + if ((cdp->cdp_flags & CDP_UNREF_DTR) != 0) + return; + cdp->cdp_flags |= CDP_UNREF_DTR; + dev_refl(dev); devfs_destroy(dev); LIST_FOREACH(child, &dev->si_children, si_siblings) delist_dev_locked(child); @@ -1124,6 +1146,7 @@ delist_dev_locked(struct cdev *dev) void delist_dev(struct cdev *dev) { + dev_lock(); delist_dev_locked(dev); dev_unlock();