Date: Wed, 14 Jan 2015 22:07:13 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r277199 - in head/sys: fs/devfs kern Message-ID: <201501142207.t0EM7Dfn041543@svn.freebsd.org>
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Author: hselasky Date: Wed Jan 14 22:07:13 2015 New Revision: 277199 URL: https://svnweb.freebsd.org/changeset/base/277199 Log: Avoid race with "dev_rel()" when using the recently added "delist_dev()" function. Make sure the character device structure doesn't go away until the end of the "destroy_dev()" function due to concurrently running cleanup code inside "devfs_populate()". MFC after: 1 week Reported by: dchagin@ Modified: head/sys/fs/devfs/devfs_devs.c head/sys/kern/kern_conf.c Modified: head/sys/fs/devfs/devfs_devs.c ============================================================================== --- head/sys/fs/devfs/devfs_devs.c Wed Jan 14 22:05:57 2015 (r277198) +++ head/sys/fs/devfs/devfs_devs.c Wed Jan 14 22:07:13 2015 (r277199) @@ -137,6 +137,12 @@ 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/kern/kern_conf.c ============================================================================== --- head/sys/kern/kern_conf.c Wed Jan 14 22:05:57 2015 (r277198) +++ head/sys/kern/kern_conf.c Wed Jan 14 22:07:13 2015 (r277199) @@ -1048,8 +1048,6 @@ destroy_devl(struct cdev *dev) /* Remove name marking */ dev->si_flags &= ~SI_NAMED; - dev->si_refcount++; /* Avoid race with dev_rel() */ - /* If we are a child, remove us from the parents list */ if (dev->si_flags & SI_CHILD) { LIST_REMOVE(dev, si_siblings);
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