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