Changeset a7e04d16 in mainline

Timestamp:

2010-12-23T00:19:59Z (14 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

23cdcc6f

Parents:

9476f4f

git-author:

Vojtech Horky <> (2010-12-23 00:19:59)

git-committer:

Jakub Jermar <jakub@…> (2010-12-23 00:19:59)

Message:

Do not hold the devices_mutex while connecting to the device in
devfs_node_open().

File:

• uspace/srv/fs/devfs/devfs_ops.c (modified) (7 diffs)

uspace/srv/fs/devfs/devfs_ops.c

@@ -60 +60 @@
 typedef struct {
         devmap_handle_t handle;
-        int phone;
+        int phone;              /**< When < 0, the structure is incomplete. */
         size_t refcount;
         link_t link;
+        fibril_condvar_t cv;    /**< Broadcast when completed. */
 } device_t;
 
@@ -227 +228 @@
                         [DEVICES_KEY_HANDLE] = (unsigned long) node->handle
                 };
-                
+                link_t *lnk;
+
                 fibril_mutex_lock(&devices_mutex);
-                link_t *lnk = hash_table_find(&devices, key);
+restart:
+                lnk = hash_table_find(&devices, key);
                 if (lnk == NULL) {
                         device_t *dev = (device_t *) malloc(sizeof(device_t));
@@ -237 +240 @@
                         }
                         
+                        dev->handle = node->handle;
+                        dev->phone = -1;        /* mark as incomplete */
+                        dev->refcount = 1;
+                        fibril_condvar_initialize(&dev->cv);
+
+                        /*
+                         * Insert the incomplete device structure so that other
+                         * fibrils will not race with us when we drop the mutex
+                         * below.
+                         */
+                        hash_table_insert(&devices, key, &dev->link);
+
+                        /*
+                         * Drop the mutex to allow recursive devfs requests.
+                         */
+                        fibril_mutex_unlock(&devices_mutex);
+
                         int phone = devmap_device_connect(node->handle, 0);
+
+                        fibril_mutex_lock(&devices_mutex);
+
+                        /*
+                         * Notify possible waiters about this device structure
+                         * being completed (or destroyed).
+                         */
+                        fibril_condvar_broadcast(&dev->cv);
+
                         if (phone < 0) {
+                                /*
+                                 * Connecting failed, need to remove the
+                                 * entry and free the device structure.
+                                 */
+                                hash_table_remove(&devices, key, DEVICES_KEYS);
                                 fibril_mutex_unlock(&devices_mutex);
+
                                 free(dev);
                                 return ENOENT;
                         }
                         
-                        dev->handle = node->handle;
+                        /* Set the correct phone. */
                         dev->phone = phone;
-                        dev->refcount = 1;
-                        
-                        hash_table_insert(&devices, key, &dev->link);
                 } else {
                         device_t *dev = hash_table_get_instance(lnk, device_t, link);
+
+                        if (dev->phone < 0) {
+                                /*
+                                 * Wait until the device structure is completed
+                                 * and start from the beginning as the device
+                                 * structure might have entirely disappeared
+                                 * while we were not holding the mutex in
+                                 * fibril_condvar_wait().
+                                 */
+                                fibril_condvar_wait(&dev->cv, &devices_mutex);
+                                goto restart;
+                        }
+
                         dev->refcount++;
                 }
@@ -564 +609 @@
                 
                 device_t *dev = hash_table_get_instance(lnk, device_t, link);
+                assert(dev->phone >= 0);
                 
                 ipc_callid_t callid;
@@ -627 +673 @@
                 
                 device_t *dev = hash_table_get_instance(lnk, device_t, link);
+                assert(dev->phone >= 0);
                 
                 ipc_callid_t callid;
@@ -696 +743 @@
                 
                 device_t *dev = hash_table_get_instance(lnk, device_t, link);
+                assert(dev->phone >= 0);
                 dev->refcount--;
                 
@@ -743 +791 @@
                 
                 device_t *dev = hash_table_get_instance(lnk, device_t, link);
+                assert(dev->phone >= 0);
                 
                 /* Make a request at the driver */