From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:46301) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gx4IV-0006rG-82 for qemu-devel@nongnu.org; Fri, 22 Feb 2019 01:27:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gx4IS-0003HY-Vq for qemu-devel@nongnu.org; Fri, 22 Feb 2019 01:26:58 -0500 Received: from mail-qt1-f195.google.com ([209.85.160.195]:40292) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gx4IQ-00027t-Tn for qemu-devel@nongnu.org; Fri, 22 Feb 2019 01:26:56 -0500 Received: by mail-qt1-f195.google.com with SMTP id j36so1347639qta.7 for ; Thu, 21 Feb 2019 22:25:31 -0800 (PST) MIME-Version: 1.0 References: <20190222031413.20250-1-peterx@redhat.com> <20190222031413.20250-2-peterx@redhat.com> In-Reply-To: <20190222031413.20250-2-peterx@redhat.com> From: =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= Date: Fri, 22 Feb 2019 07:25:16 +0100 Message-ID: Content-Type: text/plain; charset="UTF-8" Subject: Re: [Qemu-devel] [PATCH 1/4] iothread: replace init_done_cond with a semaphore List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: qemu-devel , Paolo Bonzini , Stefan Hajnoczi , Eric Blake Hi On Fri, Feb 22, 2019 at 4:14 AM Peter Xu wrote: > > 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 The lock is also protecting thread_id. > --- > 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 8a7ac2c528..50411ba54a 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 e615b7ae52..6e297e9ef1 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); > @@ -115,6 +113,7 @@ 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) > @@ -123,10 +122,6 @@ 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 > @@ -145,6 +140,7 @@ 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) > @@ -173,8 +169,6 @@ 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 > @@ -188,12 +182,9 @@ 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 { > -- > 2.17.1 >