[Qemu-devel] [PATCH] trace: add glib 2.32+ static GMutex support

[Stefan Hajnoczi <stefanha@redhat.com>]

The GStaticMutex API was deprecated in glib 2.32.  We cannot switch over
to GMutex unconditionally since we would drop support for older glib
versions.  But the deprecated API warnings during build are annoying so
use static GMutex when possible.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 trace/simple.c | 45 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/trace/simple.c b/trace/simple.c
index 1e3f691..941f7ea 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -39,7 +39,11 @@
  * Trace records are written out by a dedicated thread.  The thread waits for
  * records to become available, writes them out, and then waits again.
  */
+#if GLIB_CHECK_VERSION(2, 32, 0)
+static GMutex trace_lock;
+#else
 static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
+#endif
 
 /* g_cond_new() was deprecated in glib 2.31 but we still need to support it */
 #if GLIB_CHECK_VERSION(2, 31, 0)
@@ -86,6 +90,34 @@ typedef struct {
 static void read_from_buffer(unsigned int idx, void *dataptr, size_t size);
 static unsigned int write_to_buffer(unsigned int idx, void *dataptr, size_t size);
 
+/* Hide changes in glib mutex APIs */
+static void lock_trace_lock(void)
+{
+#if GLIB_CHECK_VERSION(2, 32, 0)
+    g_mutex_lock(&trace_lock);
+#else
+    g_static_mutex_lock(&trace_lock);
+#endif
+}
+
+static void unlock_trace_lock(void)
+{
+#if GLIB_CHECK_VERSION(2, 32, 0)
+    g_mutex_unlock(&trace_lock);
+#else
+    g_static_mutex_unlock(&trace_lock);
+#endif
+}
+
+static GMutex *get_trace_lock_mutex(void)
+{
+#if GLIB_CHECK_VERSION(2, 32, 0)
+    return &trace_lock;
+#else
+    return g_static_mutex_get_mutex(&trace_lock);
+#endif
+}
+
 static void clear_buffer_range(unsigned int idx, size_t len)
 {
     uint32_t num = 0;
@@ -139,27 +171,26 @@ static bool get_trace_record(unsigned int idx, TraceRecord **recordptr)
  */
 static void flush_trace_file(bool wait)
 {
-    g_static_mutex_lock(&trace_lock);
+    lock_trace_lock();
     trace_available = true;
     g_cond_signal(trace_available_cond);
 
     if (wait) {
-        g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
+        g_cond_wait(trace_empty_cond, get_trace_lock_mutex());
     }
 
-    g_static_mutex_unlock(&trace_lock);
+    unlock_trace_lock();
 }
 
 static void wait_for_trace_records_available(void)
 {
-    g_static_mutex_lock(&trace_lock);
+    lock_trace_lock();
     while (!(trace_available && trace_writeout_enabled)) {
         g_cond_signal(trace_empty_cond);
-        g_cond_wait(trace_available_cond,
-                    g_static_mutex_get_mutex(&trace_lock));
+        g_cond_wait(trace_available_cond, get_trace_lock_mutex());
     }
     trace_available = false;
-    g_static_mutex_unlock(&trace_lock);
+    unlock_trace_lock();
 }
 
 static gpointer writeout_thread(gpointer opaque)
-- 
1.8.4.2