Changes in uspace/lib/c/generic/task.c [9f5cf68:1c635d6] in mainline

File:

• uspace/lib/c/generic/task.c (modified) (16 diffs)

uspace/lib/c/generic/task.c

@@ -2 +2 @@
  * Copyright (c) 2006 Jakub Jermar
  * Copyright (c) 2008 Jiri Svoboda
+ * Copyright (c) 2014 Martin Sucha
  * All rights reserved.
  *
@@ -94 +95 @@
  *
  * @param id   If not NULL, the ID of the task is stored here on success.
+ * @param wait If not NULL, setup waiting for task's return value and store
+ *             the information necessary for waiting here on success.
  * @param path Pathname of the binary to execute.
  * @param argv Command-line arguments.
@@ -100 +103 @@
  *
  */
-int task_spawnv(task_id_t *id, const char *path, const char *const args[])
+int task_spawnv(task_id_t *id, task_wait_t *wait, const char *path,
+    const char *const args[])
 {
         /* Send default files */
@@ -125 +129 @@
         files[3] = NULL;
         
-        return task_spawnvf(id, path, args, files);
+        return task_spawnvf(id, wait, path, args, files);
 }
 
@@ -135 +139 @@
  *
  * @param id    If not NULL, the ID of the task is stored here on success.
+ * @param wait  If not NULL, setup waiting for task's return value and store
+ *              the information necessary for waiting here on success.
  * @param path  Pathname of the binary to execute.
  * @param argv  Command-line arguments.
@@ -142 +148 @@
  *
  */
-int task_spawnvf(task_id_t *id, const char *path, const char *const args[],
-    int *const files[])
+int task_spawnvf(task_id_t *id, task_wait_t *wait, const char *path,
+    const char *const args[], int *const files[])
 {
         /* Connect to a program loader. */
@@ -150 +156 @@
                 return EREFUSED;
         
+        bool wait_initialized = false;
+        
         /* Get task ID. */
         task_id_t task_id;
@@ -181 +189 @@
                 goto error;
         
+        /* Setup waiting for return value if needed */
+        if (wait) {
+                rc = task_setup_wait(task_id, wait);
+                if (rc != EOK)
+                        goto error;
+                wait_initialized = true;
+        }
+        
         /* Run it. */
         rc = loader_run(ldr);
@@ -193 +209 @@
         
 error:
+        if (wait_initialized)
+                task_cancel_wait(wait);
+        
         /* Error exit */
         loader_abort(ldr);
@@ -204 +223 @@
  *
  * @param id   If not NULL, the ID of the task is stored here on success.
+ * @param wait If not NULL, setup waiting for task's return value and store
+ *             the information necessary for waiting here on success.
  * @param path Pathname of the binary to execute.
  * @param cnt  Number of arguments.
@@ -211 +232 @@
  *
  */
-int task_spawn(task_id_t *task_id, const char *path, int cnt, va_list ap)
+int task_spawn(task_id_t *task_id, task_wait_t *wait, const char *path,
+    int cnt, va_list ap)
 {
         /* Allocate argument list. */
@@ -227 +249 @@
         
         /* Spawn task. */
-        int rc = task_spawnv(task_id, path, arglist);
+        int rc = task_spawnv(task_id, wait, path, arglist);
         
         /* Free argument list. */
@@ -240 +262 @@
  *
  * @param id   If not NULL, the ID of the task is stored here on success.
+ * @param wait If not NULL, setup waiting for task's return value and store
+ *             the information necessary for waiting here on success.
  * @param path Pathname of the binary to execute.
  * @param ...  Command-line arguments.
@@ -246 +270 @@
  *
  */
-int task_spawnl(task_id_t *task_id, const char *path, ...)
+int task_spawnl(task_id_t *task_id, task_wait_t *wait, const char *path, ...)
 {
         /* Count the number of arguments. */
@@ -262 +286 @@
         
         va_start(ap, path);
-        int rc = task_spawn(task_id, path, cnt, ap);
+        int rc = task_spawn(task_id, wait, path, cnt, ap);
         va_end(ap);
         
@@ -268 +292 @@
 }
 
-int task_wait(task_id_t id, task_exit_t *texit, int *retval)
+/** Setup waiting for a task.
+ * 
+ * If the task finishes after this call succeeds, it is guaranteed that
+ * task_wait(wait, &texit, &retval) will return correct return value for
+ * the task.
+ *
+ * @param id   ID of the task to setup waiting for.
+ * @param wait Information necessary for the later task_wait call is stored here.
+ *
+ * @return EOK on success, else error code.
+ */
+int task_setup_wait(task_id_t id, task_wait_t *wait)
+{
+        async_exch_t *exch = async_exchange_begin(session_ns);
+        wait->aid = async_send_2(exch, NS_TASK_WAIT, LOWER32(id), UPPER32(id),
+            &wait->result);
+        async_exchange_end(exch);
+
+        return EOK;
+}
+
+/** Cancel waiting for a task.
+ *
+ * This can be called *instead of* task_wait if the caller is not interested
+ * in waiting for the task anymore.
+ *
+ * This function cannot be called if the task_wait was already called.
+ *
+ * @param wait task_wait_t previously initialized by task_setup_wait.
+ */
+void task_cancel_wait(task_wait_t *wait) {
+        async_forget(wait->aid);
+}
+
+/** Wait for a task to finish.
+ *
+ * This function returns correct values even if the task finished in
+ * between task_setup_wait and this task_wait call.
+ *
+ * This function cannot be called more than once with the same task_wait_t
+ * (it can be reused, but must be reinitialized with task_setup_wait first)
+ *
+ * @param wait   task_wait_t previously initialized by task_setup_wait.
+ * @param texit  Store type of task exit here.
+ * @param retval Store return value of the task here.
+ * 
+ * @return EOK on success, else error code.
+ */
+int task_wait(task_wait_t *wait, task_exit_t *texit, int *retval)
 {
         assert(texit);
         assert(retval);
-        
-        async_exch_t *exch = async_exchange_begin(session_ns);
-        sysarg_t te, rv;
-        int rc = (int) async_req_2_2(exch, NS_TASK_WAIT, LOWER32(id),
-            UPPER32(id), &te, &rv);
-        async_exchange_end(exch);
-        
-        *texit = te;
-        *retval = rv;
-        
-        return rc;
+
+        sysarg_t rc;
+        async_wait_for(wait->aid, &rc);
+
+        if (rc == EOK) {
+                *texit = IPC_GET_ARG1(wait->result);
+                *retval = IPC_GET_ARG2(wait->result);
+        }
+
+        return rc;
+}
+
+/** Wait for a task to finish by its id.
+ *
+ * Note that this will fail with ENOENT if the task id is not registered in ns
+ * (e.g. if the task finished). If you are spawning a task and need to wait
+ * for its completion, use wait parameter of the task_spawn* functions instead
+ * to prevent a race where the task exits before you may have a chance to wait
+ * wait for it.
+ *
+ * @param id ID of the task to wait for.
+ * @param texit  Store type of task exit here.
+ * @param retval Store return value of the task here.
+ * 
+ * @return EOK on success, else error code.
+ */
+int task_wait_task_id(task_id_t id, task_exit_t *texit, int *retval)
+{
+        task_wait_t wait;
+        int rc = task_setup_wait(id, &wait);
+        if (rc != EOK)
+                return rc;
+        
+        return task_wait(&wait, texit, retval);
 }