[Qemu-devel] [RFC 01/10] exec: Introduce tcg_exclusive_{lock, unlock}()

[Alvise Rigo <a.rigo@virtualopensystems.com>]

Add tcg_exclusive_{lock,unlock}() functions that will be used for making
the emulation of LL and SC instructions thread safe.

Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>
---
 cpus.c            |  2 ++
 exec.c            | 18 ++++++++++++++++++
 include/qom/cpu.h |  5 +++++
 3 files changed, 25 insertions(+)

diff --git a/cpus.c b/cpus.c
index 860e7ba..b9ec903 100644
--- a/cpus.c
+++ b/cpus.c
@@ -961,6 +961,8 @@ void qemu_init_cpu_loop(void)
     qemu_cond_init(&qemu_work_cond);
     qemu_mutex_init(&qemu_global_mutex);
 
+    qemu_spin_init(&cpu_exclusive_lock);
+
     qemu_thread_get_self(&io_thread);
 
     safe_work = g_array_sized_new(TRUE, TRUE, sizeof(qemu_safe_work_item), 128);
diff --git a/exec.c b/exec.c
index a24b31c..1c72113 100644
--- a/exec.c
+++ b/exec.c
@@ -197,6 +197,24 @@ void cpu_exclusive_history_free(void)
         g_free(excl_history.c_array);
     }
 }
+
+__thread bool cpu_have_exclusive_lock;
+QemuSpin cpu_exclusive_lock;
+inline void tcg_exclusive_lock(void)
+{
+    if (!cpu_have_exclusive_lock) {
+        qemu_spin_lock(&cpu_exclusive_lock);
+        cpu_have_exclusive_lock = true;
+    }
+}
+
+inline void tcg_exclusive_unlock(void)
+{
+    if (cpu_have_exclusive_lock) {
+        cpu_have_exclusive_lock = false;
+        qemu_spin_unlock(&cpu_exclusive_lock);
+    }
+}
 #endif
 
 #if !defined(CONFIG_USER_ONLY)
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 0f51870..019f06d 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -201,6 +201,11 @@ typedef struct CPUClass {
     void (*disas_set_info)(CPUState *cpu, disassemble_info *info);
 } CPUClass;
 
+/* Protect cpu_exclusive_* variable .*/
+void tcg_exclusive_lock(void);
+void tcg_exclusive_unlock(void);
+extern QemuSpin cpu_exclusive_lock;
+
 #ifdef HOST_WORDS_BIGENDIAN
 typedef struct icount_decr_u16 {
     uint16_t high;
-- 
2.8.3