Changeset 5bee897 in mainline

Timestamp:

2010-11-30T13:42:11Z (14 years ago)

Author:

Vojtech Horky <vojtechhorky@…>

Branches:

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

Children:

703d19c

Parents:

1b2981aa

Message:

Fix deadlock in devman

The driver mutex is released during device adding to release the
deadlock when adding child device driven by the same task.

Location:

uspace/srv/devman

Files:

• devman.c (modified) (8 diffs)
• devman.h (modified) (1 diff)

uspace/srv/devman/devman.c

@@ -508 +508 @@
 /** Notify driver about the devices to which it was assigned.
  *
- * The driver's mutex must be locked.
- *
  * @param driver        The driver to which the devices are passed.
  */
@@ -520 +518 @@
         printf(NAME ": pass_devices_to_driver\n");
 
+        fibril_mutex_lock(&driver->driver_mutex);
+
         phone = ipc_connect_me_to(driver->phone, DRIVER_DEVMAN, 0, 0);
-        if (phone > 0) {
-                
+
+        if (phone < 0) {
+                fibril_mutex_unlock(&driver->driver_mutex);
+                return;
+        }
+
+        /*
+         * Go through devices list as long as there is some device
+         * that has not been passed to the driver.
+         */
+        link = driver->devices.next;
+        while (link != &driver->devices) {
+                dev = list_get_instance(link, node_t, driver_devices);
+                if (dev->passed_to_driver) {
+                        link = link->next;
+                        continue;
+                }
+
+                /*
+                 * Unlock to avoid deadlock when adding device
+                 * handled by itself.
+                 */
+                fibril_mutex_unlock(&driver->driver_mutex);
+
+                add_device(phone, driver, dev, tree);
+
+                /*
+                 * Lock again as we will work with driver's
+                 * structure.
+                 */
+                fibril_mutex_lock(&driver->driver_mutex);
+
+                /*
+                 * Restart the cycle to go through all devices again.
+                 */
                 link = driver->devices.next;
-                while (link != &driver->devices) {
-                        dev = list_get_instance(link, node_t, driver_devices);
-                        add_device(phone, driver, dev, tree);
-                        link = link->next;
-                }
-                
-                ipc_hangup(phone);
-        }
+        }
+
+        ipc_hangup(phone);
+
+        /*
+         * Once we passed all devices to the driver, we need to mark the
+         * driver as running.
+         * It is vital to do it here and inside critical section.
+         *
+         * If we would change the state earlier, other devices added to
+         * the driver would be added to the device list and started
+         * immediately and possibly started here as well.
+         */
+        driver->state = DRIVER_RUNNING;
+
+        fibril_mutex_unlock(&driver->driver_mutex);
 }
 
@@ -546 +587 @@
 {
         printf(NAME ": initialize_running_driver\n");
-        fibril_mutex_lock(&driver->driver_mutex);
         
         /*
@@ -553 +593 @@
          */
         pass_devices_to_driver(driver, tree);
-        
-        /* Change driver's state to running. */
-        driver->state = DRIVER_RUNNING;
-        
-        fibril_mutex_unlock(&driver->driver_mutex);
 }
 
@@ -637 +672 @@
 void add_device(int phone, driver_t *drv, node_t *node, dev_tree_t *tree)
 {
-        printf(NAME ": add_device\n");
+        /*
+         * We do not expect to have driver's mutex locked as we do not
+         * access any structures that would affect driver_t.
+         */
+        printf(NAME ": add_device (driver `%s', device `%s')\n", drv->name,
+            node->name);
         
         ipcarg_t rc;
@@ -649 +689 @@
                 parent_handle = 0;
         }
+
         aid_t req = async_send_2(phone, DRIVER_ADD_DEVICE, node->handle,
             parent_handle, &answer);
@@ -661 +702 @@
         /* Wait for answer from the driver. */
         async_wait_for(req, &rc);
+
         switch(rc) {
         case EOK:
@@ -673 +715 @@
         }
         
+        node->passed_to_driver = true;
+
         return;
 }

uspace/srv/devman/devman.h

@@ -168 +168 @@
          */
         link_t devmap_link;
+
+        /**
+         * Whether this device was already passed to the driver.
+         */
+        bool passed_to_driver;
 };