xnu-3789.1.32.tar.gz

[apple/xnu.git] / bsd / miscfs / devfs / devfs_tree.c

diff --git a/bsd/miscfs/devfs/devfs_tree.c b/bsd/miscfs/devfs/devfs_tree.c
index d8f3ae088c5bfe8206bc68e5df15a9a71f90b605..21912549a05ec9c325c7c5c1015cd87395283a3a 100644 (file)
--- a/bsd/miscfs/devfs/devfs_tree.c
+++ b/bsd/miscfs/devfs/devfs_tree.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2014 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
@@ -148,6 +148,7 @@ lck_grp_t   * devfs_lck_grp;
 lck_grp_attr_t * devfs_lck_grp_attr;
 lck_attr_t     * devfs_lck_attr;
 lck_mtx_t        devfs_mutex;
+lck_mtx_t        devfs_attr_mutex;
 
 devdirent_t *          dev_root = NULL;        /* root of backing tree */
 struct devfs_stats     devfs_stats;            /* hold stats */
@@ -185,6 +186,7 @@ devfs_sinit(void)
        devfs_lck_attr = lck_attr_alloc_init();
 
        lck_mtx_init(&devfs_mutex, devfs_lck_grp, devfs_lck_attr);
+       lck_mtx_init(&devfs_attr_mutex, devfs_lck_grp, devfs_lck_attr);
 
        DEVFS_LOCK();
         error = dev_add_entry("root", NULL, DEV_DIR, NULL, NULL, NULL, &dev_root);
@@ -1050,12 +1052,12 @@ dev_free_name(devdirent_t * dirent_p)
                        if(dnp->dn_linklist == dirent_p) {
                                dnp->dn_linklist = dirent_p->de_nextlink;
                        }
-                       dirent_p->de_nextlink->de_prevlinkp 
-                           = dirent_p->de_prevlinkp;
-                       *dirent_p->de_prevlinkp = dirent_p->de_nextlink;
                }
                devfs_dn_free(dnp);
        }
+       
+       dirent_p->de_nextlink->de_prevlinkp = dirent_p->de_prevlinkp;
+       *(dirent_p->de_prevlinkp) = dirent_p->de_nextlink;
 
        /*
         * unlink ourselves from the directory on this plane
@@ -1127,6 +1129,7 @@ devfs_dntovn(devnode_t * dnp, struct vnode **vn_pp, __unused struct proc * p)
        struct vnode_fsparam vfsp;
        enum vtype vtype = 0;
        int markroot = 0;
+       int nretries = 0;
        int n_minor = DEVFS_CLONE_ALLOC; /* new minor number for clone device */
        
        /*
@@ -1153,7 +1156,16 @@ retry:
 
                DEVFS_UNLOCK();
 
-               error = vnode_getwithvid(vn_p, vid);
+               /*
+                * We want to use the drainok variant of vnode_getwithvid
+                * because we _don't_ want to get an iocount if the vnode is
+                * is blocked in vnode_drain as it can cause infinite
+                * loops in vn_open_auth. While in use vnodes are typically
+                * only reclaimed on forced unmounts, In use devfs tty vnodes
+                * can  be quite frequently reclaimed by revoke(2) or by the
+                * exit of a controlling process.
+                */
+               error = vnode_getwithvid_drainok(vn_p, vid);
 
                DEVFS_LOCK();
 
@@ -1177,6 +1189,29 @@ retry:
                         * vnode.  Therefore, ENOENT is a valid result.
                         */
                        error = ENOENT;
+               } else if (error == ENODEV) {
+                       /*
+                        * The Filesystem is getting unmounted.
+                        */
+                       error = ENOENT;
+               } else if (error && (nretries < DEV_MAX_VNODE_RETRY)) {
+                       /*
+                        * If we got an error from vnode_getwithvid, it means
+                        * we raced with a recycle and lost i.e. we asked for
+                        * an iocount only after vnode_drain had been entered
+                        * for the vnode and returned with an error only after
+                        * devfs_reclaim was called on the vnode.  devfs_reclaim
+                        * sets dn_vn to NULL but while we were waiting to
+                        * reacquire DEVFS_LOCK, another vnode might have gotten
+                        * associated with the dnp. In either case, we need to
+                        * retry otherwise we will end up returning an ENOENT
+                        * for this lookup but the next lookup will  succeed
+                        * because it creates a new vnode (or a racing  lookup
+                        * created a new vnode already).
+                        */
+                       error = 0;
+                       nretries++;
+                       goto retry;
                }
                if ( !error)
                        *vn_pp = vn_p;