From 9db6f24509ee8a28818693d6a15257b873d9422a Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 15 Aug 2019 13:23:11 +0100
Subject: [PATCH 09/10] iothread: replace init_done_cond with a semaphore

RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: <20190815132311.22027-3-stefanha@redhat.com>
Patchwork-id: 89996
O-Subject: [RHEL-8.1.0 qemu-kvm PATCH v2 2/2] iothread: replace init_done_cond with a semaphore
Bugzilla: 1687541
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Markus Armbruster <armbru@redhat.com>

From: Peter Xu <peterx@redhat.com>

Only sending an init-done message using lock+cond seems an overkill to
me.  Replacing it with a simpler semaphore.

Meanwhile, init the semaphore unconditionally, then we can destroy it
unconditionally too in finalize which seems cleaner.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-id: 20190306115532.23025-2-peterx@redhat.com
Message-Id: <20190306115532.23025-2-peterx@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 21c4d15b4708b7d30c450041a560df670f36cac8)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 include/sysemu/iothread.h |  3 +--
 iothread.c                | 17 ++++-------------
 2 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h
index 8a7ac2c..50411ba 100644
--- a/include/sysemu/iothread.h
+++ b/include/sysemu/iothread.h
@@ -27,8 +27,7 @@ typedef struct {
     GMainContext *worker_context;
     GMainLoop *main_loop;
     GOnce once;
-    QemuMutex init_done_lock;
-    QemuCond init_done_cond;    /* is thread initialization done? */
+    QemuSemaphore init_done_sem; /* is thread init done? */
     bool stopping;              /* has iothread_stop() been called? */
     bool running;               /* should iothread_run() continue? */
     int thread_id;
diff --git a/iothread.c b/iothread.c
index 2fb1cdf..b92232f 100644
--- a/iothread.c
+++ b/iothread.c
@@ -55,10 +55,8 @@ static void *iothread_run(void *opaque)
     rcu_register_thread();
 
     my_iothread = iothread;
-    qemu_mutex_lock(&iothread->init_done_lock);
     iothread->thread_id = qemu_get_thread_id();
-    qemu_cond_signal(&iothread->init_done_cond);
-    qemu_mutex_unlock(&iothread->init_done_lock);
+    qemu_sem_post(&iothread->init_done_sem);
 
     while (iothread->running) {
         aio_poll(iothread->ctx, true);
@@ -111,6 +109,7 @@ static void iothread_instance_init(Object *obj)
 
     iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
     iothread->thread_id = -1;
+    qemu_sem_init(&iothread->init_done_sem, 0);
 }
 
 static void iothread_instance_finalize(Object *obj)
@@ -119,10 +118,6 @@ static void iothread_instance_finalize(Object *obj)
 
     iothread_stop(iothread);
 
-    if (iothread->thread_id != -1) {
-        qemu_cond_destroy(&iothread->init_done_cond);
-        qemu_mutex_destroy(&iothread->init_done_lock);
-    }
     /*
      * Before glib2 2.33.10, there is a glib2 bug that GSource context
      * pointer may not be cleared even if the context has already been
@@ -141,6 +136,7 @@ static void iothread_instance_finalize(Object *obj)
         g_main_context_unref(iothread->worker_context);
         iothread->worker_context = NULL;
     }
+    qemu_sem_destroy(&iothread->init_done_sem);
 }
 
 static void iothread_complete(UserCreatable *obj, Error **errp)
@@ -169,8 +165,6 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
         return;
     }
 
-    qemu_mutex_init(&iothread->init_done_lock);
-    qemu_cond_init(&iothread->init_done_cond);
     iothread->once = (GOnce) G_ONCE_INIT;
 
     /* This assumes we are called from a thread with useful CPU affinity for us
@@ -184,12 +178,9 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
     g_free(name);
 
     /* Wait for initialization to complete */
-    qemu_mutex_lock(&iothread->init_done_lock);
     while (iothread->thread_id == -1) {
-        qemu_cond_wait(&iothread->init_done_cond,
-                       &iothread->init_done_lock);
+        qemu_sem_wait(&iothread->init_done_sem);
     }
-    qemu_mutex_unlock(&iothread->init_done_lock);
 }
 
 typedef struct {
-- 
1.8.3.1