From 1b58a75f42110e95804d50ef2eba9c0c93984dc0 Mon Sep 17 00:00:00 2001
From: Johan Wikman <johan.wikman@mariadb.com>
Date: Sat, 29 Apr 2017 08:22:32 +0300
Subject: [PATCH] Add concurrent execution helper to Worker

Concurrently executing a task on all workers *and* waiting until
all workers have executed the task seems to be common enough to
warrant a helper function for that purpose.
---
 server/core/maxscale/worker.hh | 10 ++++++++++
 server/core/worker.cc          |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/server/core/maxscale/worker.hh b/server/core/maxscale/worker.hh
index e2fa1c72b..859ae9847 100644
--- a/server/core/maxscale/worker.hh
+++ b/server/core/maxscale/worker.hh
@@ -338,6 +338,16 @@ public:
      */
     static size_t execute_on_all_serially(Task* pTask);
 
+    /**
+     * Executes a task on all workers concurrently and waits until
+     * all workers are done.
+     *
+     * @param pTask  The task to be executed.
+     *
+     * @return How many workers the task was posted to.
+     */
+    static size_t execute_on_all_concurrently(Task* pTask);
+
     /**
      * Post a message to a worker.
      *
diff --git a/server/core/worker.cc b/server/core/worker.cc
index 4b3e5ac1f..5f5ec135c 100644
--- a/server/core/worker.cc
+++ b/server/core/worker.cc
@@ -618,6 +618,7 @@ size_t Worker::execute_on_all(std::auto_ptr<DisposableTask> sTask)
 
     return n;
 }
+
 //static
 size_t Worker::execute_on_all_serially(Task* pTask)
 {
@@ -638,6 +639,13 @@ size_t Worker::execute_on_all_serially(Task* pTask)
     return n;
 }
 
+//static
+size_t Worker::execute_on_all_concurrently(Task* pTask)
+{
+    Semaphore sem;
+    return sem.wait_n(Worker::execute_on_all(pTask, &sem));
+}
+
 bool Worker::post_message(uint32_t msg_id, intptr_t arg1, intptr_t arg2)
 {
     // NOTE: No logging here, this function must be signal safe.