[Qemu-devel] [PATCH 03/12] make SIG_IPI to tcg vcpu thread reliable

[Marcelo Tosatti]

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: Marcelo Tosatti <address@hidden>
Signed-off-by: Avi Kivity <address@hidden>
---
 cpu-exec.c |    7 +++++++
 cpus.c     |   23 +++++++++--------------
 exec-all.h |    3 +++
 3 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/cpu-exec.c b/cpu-exec.c
index dc81e79..c776605 100644
--- a/cpu-exec.c
+++ b/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 */
diff --git a/cpus.c b/cpus.c
index 29462e5..53226b3 100644
--- a/cpus.c
+++ b/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)
diff --git a/exec-all.h b/exec-all.h
index 1016de2..4565dd0 100644
--- a/exec-all.h
+++ b/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
-- 
1.6.6.1