[Qemu-devel] [PATCH 1/6] Enable joinable POSIX threads

[Jan Kiszka]

Allow to control if a QEMU thread is created joinable or not. Make it
not joinable by default to avoid that we keep the associated resources
around when terminating a thread without joining it (what we couldn't do
so far for obvious reasons).

The audio subsystem will need the join feature when converting it to
QEMU threading/locking abstractions, so provide that service. Join will
only be provided for POSIX as there is no setup in sight yet where
Windows would need it as well (+implementation is non-trivial).

Signed-off-by: Jan Kiszka <address@hidden>
---
 cpus.c                  |    6 ++++--
 hw/ccid-card-emulated.c |    5 +++--
 qemu-thread-posix.c     |   31 +++++++++++++++++++++++++++----
 qemu-thread-posix.h     |    3 +++
 qemu-thread-win32.c     |    4 +++-
 qemu-thread.h           |    7 +++++--
 ui/vnc-jobs-async.c     |    2 +-
 7 files changed, 46 insertions(+), 12 deletions(-)

diff --git a/cpus.c b/cpus.c
index d0cfe91..3f7724a 100644
--- a/cpus.c
+++ b/cpus.c
@@ -822,7 +822,8 @@ static void qemu_tcg_init_vcpu(void *_env)
         env->halt_cond = g_malloc0(sizeof(QemuCond));
         qemu_cond_init(env->halt_cond);
         tcg_halt_cond = env->halt_cond;
-        qemu_thread_create(env->thread, qemu_tcg_cpu_thread_fn, env);
+        qemu_thread_create(env->thread, qemu_tcg_cpu_thread_fn, env,
+                           QEMU_THREAD_DETACHED);
         while (env->created == 0) {
             qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
         }
@@ -838,7 +839,8 @@ static void qemu_kvm_start_vcpu(CPUState *env)
     env->thread = g_malloc0(sizeof(QemuThread));
     env->halt_cond = g_malloc0(sizeof(QemuCond));
     qemu_cond_init(env->halt_cond);
-    qemu_thread_create(env->thread, qemu_kvm_cpu_thread_fn, env);
+    qemu_thread_create(env->thread, qemu_kvm_cpu_thread_fn, env,
+                       QEMU_THREAD_DETACHED);
     while (env->created == 0) {
         qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
     }
diff --git a/hw/ccid-card-emulated.c b/hw/ccid-card-emulated.c
index 092301b..9fe9db5 100644
--- a/hw/ccid-card-emulated.c
+++ b/hw/ccid-card-emulated.c
@@ -541,8 +541,9 @@ static int emulated_initfn(CCIDCardState *base)
         printf("%s: failed to initialize vcard\n", EMULATED_DEV_NAME);
         return -1;
     }
-    qemu_thread_create(&thread_id, event_thread, card);
-    qemu_thread_create(&thread_id, handle_apdu_thread, card);
+    qemu_thread_create(&thread_id, event_thread, card, QEMU_THREAD_DETACHED);
+    qemu_thread_create(&thread_id, handle_apdu_thread, card,
+                       QEMU_THREAD_DETACHED);
     return 0;
 }
 
diff --git a/qemu-thread-posix.c b/qemu-thread-posix.c
index 2bd02ef..f76427e 100644
--- a/qemu-thread-posix.c
+++ b/qemu-thread-posix.c
@@ -117,20 +117,33 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
 
 void qemu_thread_create(QemuThread *thread,
                        void *(*start_routine)(void*),
-                       void *arg)
+                       void *arg, int mode)
 {
+    sigset_t set, oldset;
+    pthread_attr_t attr;
     int err;
 
-    /* Leave signal handling to the iothread.  */
-    sigset_t set, oldset;
+    err = pthread_attr_init(&attr);
+    if (err) {
+        error_exit(err, __func__);
+    }
+    if (mode == QEMU_THREAD_DETACHED) {
+        err = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+        if (err) {
+            error_exit(err, __func__);
+        }
+    }
 
+    /* Leave signal handling to the iothread.  */
     sigfillset(&set);
     pthread_sigmask(SIG_SETMASK, &set, &oldset);
-    err = pthread_create(&thread->thread, NULL, start_routine, arg);
+    err = pthread_create(&thread->thread, &attr, start_routine, arg);
     if (err)
         error_exit(err, __func__);
 
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+
+    pthread_attr_destroy(&attr);
 }
 
 void qemu_thread_get_self(QemuThread *thread)
@@ -147,3 +160,13 @@ void qemu_thread_exit(void *retval)
 {
     pthread_exit(retval);
 }
+
+void qemu_thread_join(QemuThread *thread)
+{
+    int err;
+
+    err = pthread_join(thread->thread, NULL);
+    if (err) {
+        error_exit(err, __func__);
+    }
+}
diff --git a/qemu-thread-posix.h b/qemu-thread-posix.h
index ee4618e..540fa0b 100644
--- a/qemu-thread-posix.h
+++ b/qemu-thread-posix.h
@@ -14,4 +14,7 @@ struct QemuThread {
     pthread_t thread;
 };
 
+/* only provided for posix so far */
+void qemu_thread_join(QemuThread *thread);
+
 #endif
diff --git a/qemu-thread-win32.c b/qemu-thread-win32.c
index a27332e..4819ff4 100644
--- a/qemu-thread-win32.c
+++ b/qemu-thread-win32.c
@@ -243,10 +243,12 @@ static inline void qemu_thread_init(void)
 
 void qemu_thread_create(QemuThread *thread,
                        void *(*start_routine)(void *),
-                       void *arg)
+                       void *arg, int mode)
 {
     HANDLE hThread;
 
+    assert(mode == QEMU_THREAD_DETACHED);
+
     struct QemuThreadData *data;
     qemu_thread_init();
     data = g_malloc(sizeof *data);
diff --git a/qemu-thread.h b/qemu-thread.h
index 0a73d50..aa1ae55 100644
--- a/qemu-thread.h
+++ b/qemu-thread.h
@@ -13,6 +13,9 @@ typedef struct QemuThread QemuThread;
 #include "qemu-thread-posix.h"
 #endif
 
+#define QEMU_THREAD_JOINABLE 0
+#define QEMU_THREAD_DETACHED 1
+
 void qemu_mutex_init(QemuMutex *mutex);
 void qemu_mutex_destroy(QemuMutex *mutex);
 void qemu_mutex_lock(QemuMutex *mutex);
@@ -32,8 +35,8 @@ void qemu_cond_broadcast(QemuCond *cond);
 void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex);
 
 void qemu_thread_create(QemuThread *thread,
-                       void *(*start_routine)(void*),
-                       void *arg);
+                        void *(*start_routine)(void *),
+                        void *arg, int mode);
 void qemu_thread_get_self(QemuThread *thread);
 int qemu_thread_is_self(QemuThread *thread);
 void qemu_thread_exit(void *retval);
diff --git a/ui/vnc-jobs-async.c b/ui/vnc-jobs-async.c
index de5ea6b..9b3016c 100644
--- a/ui/vnc-jobs-async.c
+++ b/ui/vnc-jobs-async.c
@@ -318,7 +318,7 @@ void vnc_start_worker_thread(void)
         return ;
 
     q = vnc_queue_init();
-    qemu_thread_create(&q->thread, vnc_worker_thread, q);
+    qemu_thread_create(&q->thread, vnc_worker_thread, q, QEMU_THREAD_DETACHED);
     queue = q; /* Set global queue */
 }
 
-- 
1.7.3.4