Replace qemu_system_cond with VCPU stop mechanism

We can express the VCPU thread wakeup with the stop mechanism, saving
both qemu_system_ready and the qemu_system_cond. For KVM threads, we can
just enter the main loop as long as the thread is stopped. The central
TCG thread is better held back before the loop as there can be side
effects of the services called even when all CPUs are stopped.

Creating VCPUs in stopped state will also be required for proper CPU
hotplugging support.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 6 insertions, 14 deletions

diff --git a/cpus.c b/cpus.c
index b60410c403..b163efe4a8 100644
--- a/cpus.c
+++ b/cpus.c
@@ -644,11 +644,9 @@ static QemuThread io_thread;
 static QemuThread *tcg_cpu_thread;
 static QemuCond *tcg_halt_cond;
 
-static int qemu_system_ready;
 /* cpu creation */
 static QemuCond qemu_cpu_cond;
 /* system init */
-static QemuCond qemu_system_cond;
 static QemuCond qemu_pause_cond;
 static QemuCond qemu_work_cond;
 
@@ -670,7 +668,6 @@ int qemu_init_main_loop(void)
     }
 
     qemu_cond_init(&qemu_cpu_cond);
-    qemu_cond_init(&qemu_system_cond);
     qemu_cond_init(&qemu_pause_cond);
     qemu_cond_init(&qemu_work_cond);
     qemu_cond_init(&qemu_io_proceeded_cond);
@@ -684,8 +681,7 @@ int qemu_init_main_loop(void)
 
 void qemu_main_loop_start(void)
 {
-    qemu_system_ready = 1;
-    qemu_cond_broadcast(&qemu_system_cond);
+    resume_all_vcpus();
 }
 
 void run_on_cpu(CPUState *env, void (*func)(void *data), void *data)
@@ -796,11 +792,6 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
     env->created = 1;
     qemu_cond_signal(&qemu_cpu_cond);
 
-    /* and wait for machine initialization */
-    while (!qemu_system_ready) {
-        qemu_cond_wait(&qemu_system_cond, &qemu_global_mutex);
-    }
-
     while (1) {
         if (cpu_can_run(env)) {
             r = kvm_cpu_exec(env);
@@ -829,9 +820,9 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
     }
     qemu_cond_signal(&qemu_cpu_cond);
 
-    /* and wait for machine initialization */
-    while (!qemu_system_ready) {
-        qemu_cond_wait(&qemu_system_cond, &qemu_global_mutex);
+    /* wait for initial kick-off after machine start */
+    while (first_cpu->stopped) {
+        qemu_cond_wait(tcg_halt_cond, &qemu_global_mutex);
     }
 
     while (1) {
@@ -971,12 +962,12 @@ static void qemu_tcg_init_vcpu(void *_env)
         env->thread = g_malloc0(sizeof(QemuThread));
         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);
         while (env->created == 0) {
             qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
         }
         tcg_cpu_thread = env->thread;
-        tcg_halt_cond = env->halt_cond;
     } else {
         env->thread = tcg_cpu_thread;
         env->halt_cond = tcg_halt_cond;
@@ -1000,6 +991,7 @@ void qemu_init_vcpu(void *_env)
 
     env->nr_cores = smp_cores;
     env->nr_threads = smp_threads;
+    env->stopped = 1;
     if (kvm_enabled()) {
         qemu_kvm_start_vcpu(env);
     } else {