[kvm-devel] [patch 13/13] QEMU/KVM: get rid of global lock

[Marcelo Tosatti]

Now that QEMU does all necessary locking itself, get rid of the global mutex 
lock.

Allows more than one thread inside QEMU simultaneously.

Index: kvm-userspace.io/qemu/qemu-kvm.c
===================================================================
--- kvm-userspace.io.orig/qemu/qemu-kvm.c
+++ kvm-userspace.io/qemu/qemu-kvm.c
@@ -145,7 +145,6 @@ static int try_push_interrupts(void *opa
 static void post_kvm_run(void *opaque, int vcpu)
 {
 
-    pthread_mutex_lock(&qemu_mutex);
     kvm_arch_post_kvm_run(opaque, vcpu);
 }
 
@@ -157,7 +156,6 @@ static int pre_kvm_run(void *opaque, int
 
     if (env->interrupt_request & CPU_INTERRUPT_EXIT)
        return 1;
-    pthread_mutex_unlock(&qemu_mutex);
     return 0;
 }
 
@@ -228,7 +226,6 @@ static int kvm_eat_signal(struct qemu_kv
     if (r == -1 && (errno == EAGAIN || errno == EINTR) && !timeout)
        return 0;
     e = errno;
-    pthread_mutex_lock(&qemu_mutex);
     if (r == -1 && !(errno == EAGAIN || errno == EINTR)) {
        printf("sigtimedwait: %s\n", strerror(e));
        exit(1);
@@ -241,7 +238,6 @@ static int kvm_eat_signal(struct qemu_kv
        vcpu_info[env->cpu_index].stopped = 1;
        pthread_kill(io_thread, SIGUSR1);
     }
-    pthread_mutex_unlock(&qemu_mutex);
 
     return ret;
 }
@@ -264,9 +260,7 @@ static void kvm_eat_signals(CPUState *en
 
 static void kvm_main_loop_wait(CPUState *env, int timeout)
 {
-    pthread_mutex_unlock(&qemu_mutex);
     kvm_eat_signals(env, timeout);
-    pthread_mutex_lock(&qemu_mutex);
     vcpu_info[env->cpu_index].signalled = 0;
 }
 
@@ -339,7 +333,6 @@ static int kvm_main_loop_cpu(CPUState *e
     struct vcpu_info *info = &vcpu_info[env->cpu_index];
 
     setup_kernel_sigmask(env);
-    pthread_mutex_lock(&qemu_mutex);
 
     kvm_qemu_init_env(env);
     env->ready_for_interrupt_injection = 1;
@@ -367,7 +360,6 @@ static int kvm_main_loop_cpu(CPUState *e
            kvm_arch_load_regs(env);
        }
     }
-    pthread_mutex_unlock(&qemu_mutex);
     return 0;
 }
 
@@ -456,12 +448,10 @@ void qemu_kvm_notify_work(void)
 int kvm_main_loop(void)
 {
     io_thread = pthread_self();
-    pthread_mutex_unlock(&qemu_mutex);
     while (1) {
         if (get_cpu_env())
             hw_error("io thread has valid env\n");
         kvm_eat_signal(&io_signal_table, NULL, 1000);
-        pthread_mutex_lock(&qemu_mutex);
         main_loop_wait(0);
         if (qemu_shutdown_requested())
             break;
@@ -471,10 +461,8 @@ int kvm_main_loop(void)
             pthread_kill(vcpu_info[0].thread, SIG_IPI);
             qemu_kvm_reset_requested = 1;
         }
-        pthread_mutex_unlock(&qemu_mutex);
     }
 
-    pthread_mutex_unlock(&qemu_mutex);
     return 0;
 }
 
@@ -614,7 +602,6 @@ int kvm_qemu_init()
     if (!kvm_context) {
        return -1;
     }
-    pthread_mutex_lock(&qemu_mutex);
 
     return 0;
 }
@@ -833,12 +820,13 @@ void qemu_kvm_aio_wait(void)
 
     /* io thread */
     if (!env) {
-        pthread_mutex_unlock(&qemu_mutex);
         kvm_eat_signal(&io_signal_table, NULL, 1000);
-        pthread_mutex_lock(&qemu_mutex);
     /* vcpu thread */
-    } else
+    } else {
+        pthread_mutex_lock(&qemu_mutex);
         pthread_cond_wait(&qemu_aio_cond, &qemu_mutex);
+        pthread_mutex_unlock(&qemu_mutex);
+    }
 }
 
 void qemu_kvm_aio_wait_end(void)

-- 


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