qemu/main-loop: Introduce QEMU_IOTHREAD_LOCK_GUARD

Create a wrapper for locking/unlocking the iothread lock.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
index 3c9a9a982d..c25f390696 100644
--- a/include/qemu/main-loop.h
+++ b/include/qemu/main-loop.h
@@ -343,6 +343,35 @@ void qemu_mutex_lock_iothread_impl(const char *file, int line);
  */
 void qemu_mutex_unlock_iothread(void);
 
+/**
+ * QEMU_IOTHREAD_LOCK_GUARD
+ *
+ * Wrap a block of code in a conditional qemu_mutex_{lock,unlock}_iothread.
+ */
+typedef struct IOThreadLockAuto IOThreadLockAuto;
+
+static inline IOThreadLockAuto *qemu_iothread_auto_lock(const char *file,
+                                                        int line)
+{
+    if (qemu_mutex_iothread_locked()) {
+        return NULL;
+    }
+    qemu_mutex_lock_iothread_impl(file, line);
+    /* Anything non-NULL causes the cleanup function to be called */
+    return (IOThreadLockAuto *)(uintptr_t)1;
+}
+
+static inline void qemu_iothread_auto_unlock(IOThreadLockAuto *l)
+{
+    qemu_mutex_unlock_iothread();
+}
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(IOThreadLockAuto, qemu_iothread_auto_unlock)
+
+#define QEMU_IOTHREAD_LOCK_GUARD() \
+    g_autoptr(IOThreadLockAuto) _iothread_lock_auto __attribute__((unused)) \
+        = qemu_iothread_auto_lock(__FILE__, __LINE__)
+
 /*
  * qemu_cond_wait_iothread: Wait on condition for the main loop mutex
  *