vlib: add support for workers sync
Adds api that allows workers to synchronize through main thread.
Type: improvement
Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I1e75e2fb5144d397d19b13c4dfc7e937f11c044c
diff --git a/src/vlib/threads.c b/src/vlib/threads.c
index b470976..e34ef7c 100644
--- a/src/vlib/threads.c
+++ b/src/vlib/threads.c
@@ -1480,6 +1480,56 @@
vm->clib_time.last_cpu_time, 1 /* leave */ );
}
+static void
+vlib_worker_sync_rpc (void *args)
+{
+ ASSERT (vlib_thread_is_main_w_barrier ());
+ vlib_worker_threads->wait_before_barrier = 0;
+}
+
+void
+vlib_workers_sync (void)
+{
+ if (PREDICT_FALSE (!vlib_num_workers ()))
+ return;
+
+ if (!(*vlib_worker_threads->wait_at_barrier) &&
+ !clib_atomic_swap_rel_n (&vlib_worker_threads->wait_before_barrier, 1))
+ {
+ u32 thread_index = vlib_get_thread_index ();
+ vlib_rpc_call_main_thread (vlib_worker_sync_rpc, (u8 *) &thread_index,
+ sizeof (thread_index));
+ }
+
+ /* Wait until main thread asks for barrier */
+ while (!(*vlib_worker_threads->wait_at_barrier))
+ ;
+
+ /* Stop before barrier and make sure all threads are either
+ * at worker barrier or the barrier before it */
+ clib_atomic_fetch_add (&vlib_worker_threads->workers_before_barrier, 1);
+ while (vlib_num_workers () > (*vlib_worker_threads->workers_at_barrier +
+ vlib_worker_threads->workers_before_barrier))
+ ;
+}
+
+void
+vlib_workers_continue (void)
+{
+ if (PREDICT_FALSE (!vlib_num_workers ()))
+ return;
+
+ clib_atomic_fetch_add (&vlib_worker_threads->done_work_before_barrier, 1);
+
+ /* Wait until all workers are done with work before barrier */
+ while (vlib_worker_threads->done_work_before_barrier <
+ vlib_worker_threads->workers_before_barrier)
+ ;
+
+ clib_atomic_fetch_add (&vlib_worker_threads->done_work_before_barrier, -1);
+ clib_atomic_fetch_add (&vlib_worker_threads->workers_before_barrier, -1);
+}
+
/**
* Wait until each of the workers has been once around the track
*/
diff --git a/src/vlib/threads.h b/src/vlib/threads.h
index e406dde..b25d476 100644
--- a/src/vlib/threads.h
+++ b/src/vlib/threads.h
@@ -101,6 +101,9 @@
const char *barrier_caller;
const char *barrier_context;
volatile u32 *node_reforks_required;
+ volatile u32 wait_before_barrier;
+ volatile u32 workers_before_barrier;
+ volatile u32 done_work_before_barrier;
long lwp;
int cpu_id;
@@ -484,6 +487,17 @@
void vlib_get_thread_core_numa (vlib_worker_thread_t * w, unsigned cpu_id);
vlib_thread_main_t *vlib_get_thread_main_not_inline (void);
+/**
+ * Force workers sync from within worker
+ *
+ * Must be paired with @ref vlib_workers_continue
+ */
+void vlib_workers_sync (void);
+/**
+ * Release barrier after workers sync
+ */
+void vlib_workers_continue (void);
+
#endif /* included_vlib_threads_h */
/*