[dpdk-dev] [PATCH 1/2] eal: add API that sleeps while waiting for threads

[Ferruh Yigit <ferruh.yigit@intel.com>]

It is common that sample applications call rte_eal_wait_lcore() while
waiting for worker threads to be terminated.
Mostly master lcore keeps waiting in this function.

The waiting app for termination is not a time critical task, app can
prefer a sleep version of the waiting to consume less cycles.

A sleeping version of the API, rte_eal_wait_lcore_sleep(), has been
added which gets sleeping interval as parameter.

Sample applications will be updated later to use this API.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
---
 lib/librte_eal/common/eal_common_launch.c  | 22 ++++++++++++++++++
 lib/librte_eal/common/include/rte_launch.h | 27 ++++++++++++++++++++++
 lib/librte_eal/rte_eal_version.map         |  1 +
 3 files changed, 50 insertions(+)

diff --git a/lib/librte_eal/common/eal_common_launch.c b/lib/librte_eal/common/eal_common_launch.c
index fe0ba3f0d..e804c70c3 100644
--- a/lib/librte_eal/common/eal_common_launch.c
+++ b/lib/librte_eal/common/eal_common_launch.c
@@ -5,6 +5,7 @@
 #include <errno.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <unistd.h>
 #include <sys/queue.h>
 
 #include <rte_launch.h>
@@ -35,6 +36,27 @@ rte_eal_wait_lcore(unsigned slave_id)
 	return lcore_config[slave_id].ret;
 }
 
+/*
+ * Wait until a lcore finished its job by sleeping.
+ * Sleep time will be times of 'usec'
+ */
+int
+rte_eal_wait_lcore_sleep(unsigned slave_id, size_t usec)
+{
+	if (lcore_config[slave_id].state == WAIT)
+		return 0;
+
+	while (lcore_config[slave_id].state != WAIT &&
+	       lcore_config[slave_id].state != FINISHED)
+			usleep(usec);
+
+	rte_rmb();
+
+	/* we are in finished state, go to wait state */
+	lcore_config[slave_id].state = WAIT;
+	return lcore_config[slave_id].ret;
+}
+
 /*
  * Check that every SLAVE lcores are in WAIT state, then call
  * rte_eal_remote_launch() for all of them. If call_master is true
diff --git a/lib/librte_eal/common/include/rte_launch.h b/lib/librte_eal/common/include/rte_launch.h
index 06a671752..a935fd8b5 100644
--- a/lib/librte_eal/common/include/rte_launch.h
+++ b/lib/librte_eal/common/include/rte_launch.h
@@ -11,6 +11,8 @@
  * Launch tasks on other lcores
  */
 
+#include <rte_compat.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -129,6 +131,31 @@ enum rte_lcore_state_t rte_eal_get_lcore_state(unsigned slave_id);
  */
 int rte_eal_wait_lcore(unsigned slave_id);
 
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Wait until an lcore finishes its job.
+ *
+ * To be executed on the MASTER lcore only.
+ *
+ * Same as rte_eal_wait_lcore() but sleeps instead of busy wait.
+ *
+ * @param slave_id
+ *   The identifier of the lcore.
+ * @param usec
+ *   The sleep interval in microseconds
+ * @return
+ *   - 0: If the lcore identified by the slave_id is in a WAIT state.
+ *   - The value that was returned by the previous remote launch
+ *     function call if the lcore identified by the slave_id was in a
+ *     FINISHED or RUNNING state. In this case, it changes the state
+ *     of the lcore to WAIT.
+ */
+__rte_experimental int
+rte_eal_wait_lcore_sleep(unsigned slave_id, size_t usec);
+
 /**
  * Wait until all lcores finish their jobs.
  *
diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index e968edc2e..6c636a65d 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -292,6 +292,7 @@ EXPERIMENTAL {
 	rte_devargs_remove;
 	rte_devargs_type_count;
 	rte_eal_cleanup;
+	rte_eal_wait_lcore_sleep;
 	rte_fbarray_attach;
 	rte_fbarray_destroy;
 	rte_fbarray_detach;
-- 
2.17.1