make SIG_IPI to tcg vcpu thread reliable

Store tcg loop exit request on a global variable, and transfer it to
per-CPUState exit_request after assignment of cpu_single_env.

This makes exit request signal from robust. Drop the timedlock hack.
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

cpu-exec.c

@@ -213,6 +213,8 @@ static void cpu_handle_debug_exception(CPUState *env)
 
 /* main execution loop */
 
+volatile sig_atomic_t exit_request;
+
 int cpu_exec(CPUState *env1)
 {
     volatile host_reg_t saved_env_reg;
@@ -234,6 +236,11 @@ int cpu_exec(CPUState *env1)
     asm("");
     env = env1;
 
+    if (exit_request) {
+        env->exit_request = 1;
+        exit_request = 0;
+    }
+
 #if defined(TARGET_I386)
     if (!kvm_enabled()) {
         /* put eflags in CPU temporary format */

cpus.c

@@ -472,6 +472,7 @@ static void cpu_signal(int sig)
 {
     if (cpu_single_env)
         cpu_exit(cpu_single_env);
+    exit_request = 1;
 }
 
 static void tcg_block_io_signals(void)
@@ -542,26 +543,20 @@ static void unblock_io_signals(void)
     pthread_sigmask(SIG_BLOCK, &set, NULL);
 }
 
-static void qemu_signal_lock(unsigned int msecs)
-{
-    qemu_mutex_lock(&qemu_fair_mutex);
-
-    while (qemu_mutex_trylock(&qemu_global_mutex)) {
-        qemu_thread_signal(tcg_cpu_thread, SIG_IPI);
-        if (!qemu_mutex_timedlock(&qemu_global_mutex, msecs))
-            break;
-    }
-    qemu_mutex_unlock(&qemu_fair_mutex);
-}
-
 void qemu_mutex_lock_iothread(void)
 {
     if (kvm_enabled()) {
         qemu_mutex_lock(&qemu_fair_mutex);
         qemu_mutex_lock(&qemu_global_mutex);
         qemu_mutex_unlock(&qemu_fair_mutex);
-    } else
-        qemu_signal_lock(100);
+    } else {
+        qemu_mutex_lock(&qemu_fair_mutex);
+        if (qemu_mutex_trylock(&qemu_global_mutex)) {
+            qemu_thread_signal(tcg_cpu_thread, SIG_IPI);
+            qemu_mutex_lock(&qemu_global_mutex);
+        }
+        qemu_mutex_unlock(&qemu_fair_mutex);
+    }
 }
 
 void qemu_mutex_unlock_iothread(void)

exec-all.h

@@ -351,4 +351,7 @@ CPUDebugExcpHandler *cpu_set_debug_excp_handler(CPUDebugExcpHandler *handler);
 /* vl.c */
 extern int singlestep;
 
+/* cpu-exec.c */
+extern volatile sig_atomic_t exit_request;
+
 #endif