eal: simplify control thread creation

Remove the usage of pthread barrier and replace it with
synchronization using atomic variable.
This also removes the use of reference count required to synchronize
freeing the memory.

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Olivier Matz <olivier.matz@6wind.com>

diff --git a/lib/eal/common/eal_common_thread.c b/lib/eal/common/eal_common_thread.c
index 1a52f42..bb6fc80 100644 (file)
--- a/lib/eal/common/eal_common_thread.c
+++ b/lib/eal/common/eal_common_thread.c
@@ -166,38 +166,42 @@ __rte_thread_uninit(void)
        RTE_PER_LCORE(_lcore_id) = LCORE_ID_ANY;
 }
 
+enum __rte_ctrl_thread_status {
+       CTRL_THREAD_LAUNCHING, /* Yet to call pthread_create function */
+       CTRL_THREAD_RUNNING, /* Control thread is running successfully */
+       CTRL_THREAD_ERROR /* Control thread encountered an error */
+};
+
 struct rte_thread_ctrl_params {
        void *(*start_routine)(void *);
        void *arg;
-       pthread_barrier_t configured;
-       unsigned int refcnt;
+       int ret;
+       /* Control thread status.
+        * If the status is CTRL_THREAD_ERROR, 'ret' has the error code.
+        */
+       enum __rte_ctrl_thread_status ctrl_thread_status;
 };
 
-static void ctrl_params_free(struct rte_thread_ctrl_params *params)
-{
-       if (__atomic_sub_fetch(&params->refcnt, 1, __ATOMIC_ACQ_REL) == 0) {
-               (void)pthread_barrier_destroy(&params->configured);
-               free(params);
-       }
-}
-
 static void *ctrl_thread_init(void *arg)
 {
        struct internal_config *internal_conf =
                eal_get_internal_configuration();
        rte_cpuset_t *cpuset = &internal_conf->ctrl_cpuset;
        struct rte_thread_ctrl_params *params = arg;
-       void *(*start_routine)(void *);
+       void *(*start_routine)(void *) = params->start_routine;
        void *routine_arg = params->arg;
 
        __rte_thread_init(rte_lcore_id(), cpuset);
-
-       pthread_barrier_wait(&params->configured);
-       start_routine = params->start_routine;
-       ctrl_params_free(params);
-
-       if (start_routine == NULL)
+       params->ret = pthread_setaffinity_np(pthread_self(), sizeof(*cpuset),
+               cpuset);
+       if (params->ret != 0) {
+               __atomic_store_n(&params->ctrl_thread_status,
+                       CTRL_THREAD_ERROR, __ATOMIC_RELEASE);
                return NULL;
+       }
+
+       __atomic_store_n(&params->ctrl_thread_status,
+               CTRL_THREAD_RUNNING, __ATOMIC_RELEASE);
 
        return start_routine(routine_arg);
 }
@@ -207,10 +211,8 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
                const pthread_attr_t *attr,
                void *(*start_routine)(void *), void *arg)
 {
-       struct internal_config *internal_conf =
-               eal_get_internal_configuration();
-       rte_cpuset_t *cpuset = &internal_conf->ctrl_cpuset;
        struct rte_thread_ctrl_params *params;
+       enum __rte_ctrl_thread_status ctrl_thread_status;
        int ret;
 
        params = malloc(sizeof(*params));
@@ -219,15 +221,14 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
 
        params->start_routine = start_routine;
        params->arg = arg;
-       params->refcnt = 2;
-
-       ret = pthread_barrier_init(&params->configured, NULL, 2);
-       if (ret != 0)
-               goto fail_no_barrier;
+       params->ret = 0;
+       params->ctrl_thread_status = CTRL_THREAD_LAUNCHING;
 
        ret = pthread_create(thread, attr, ctrl_thread_init, (void *)params);
-       if (ret != 0)
-               goto fail_with_barrier;
+       if (ret != 0) {
+               free(params);
+               return -ret;
+       }
 
        if (name != NULL) {
                ret = rte_thread_setname(*thread, name);
@@ -236,24 +237,24 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
                                "Cannot set name for ctrl thread\n");
        }
 
-       ret = pthread_setaffinity_np(*thread, sizeof(*cpuset), cpuset);
-       if (ret != 0)
-               params->start_routine = NULL;
-
-       pthread_barrier_wait(&params->configured);
-       ctrl_params_free(params);
+       /* Wait for the control thread to initialize successfully */
+       while ((ctrl_thread_status =
+                       __atomic_load_n(&params->ctrl_thread_status,
+                       __ATOMIC_ACQUIRE)) == CTRL_THREAD_LAUNCHING) {
+               /* Yield the CPU. Using sched_yield call requires maintaining
+                * another implementation for Windows as sched_yield is not
+                * supported on Windows.
+                */
+               rte_delay_us_sleep(1);
+       }
 
-       if (ret != 0)
-               /* start_routine has been set to NULL above; */
-               /* ctrl thread will exit immediately */
+       /* Check if the control thread encountered an error */
+       if (ctrl_thread_status == CTRL_THREAD_ERROR) {
+               /* ctrl thread is exiting */
                pthread_join(*thread, NULL);
+       }
 
-       return -ret;
-
-fail_with_barrier:
-       (void)pthread_barrier_destroy(&params->configured);
-
-fail_no_barrier:
+       ret = params->ret;
        free(params);
 
        return -ret;

diff --git a/lib/eal/include/rte_lcore.h b/lib/eal/include/rte_lcore.h
index 0458d23..77a5ec5 100644 (file)
--- a/lib/eal/include/rte_lcore.h
+++ b/lib/eal/include/rte_lcore.h
@@ -405,10 +405,11 @@ rte_thread_unregister(void);
 /**
  * Create a control thread.
  *
- * Wrapper to pthread_create(), pthread_setname_np() and
- * pthread_setaffinity_np(). The affinity of the new thread is based
- * on the CPU affinity retrieved at the time rte_eal_init() was called,
- * the dataplane and service lcores are then excluded.
+ * Creates a control thread with the given name and attributes. The
+ * affinity of the new thread is based on the CPU affinity retrieved
+ * at the time rte_eal_init() was called, the dataplane and service
+ * lcores are then excluded. If setting the name of the thread fails,
+ * the error is ignored and a debug message is logged.
  *
  * @param thread
  *   Filled with the thread id of the new created thread.