[PATCH v1 1/5] Add a mutex to guarantee single writer to qemu_logfile handle.

[Robert Foley <robert.foley@linaro.org>]

Also added qemu_logfile_init() for initializing the logfile mutex.

Signed-off-by: Robert Foley <robert.foley@linaro.org>
---
v1
    - changed qemu_logfile_init() to use __constructor__.
---
 util/log.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/util/log.c b/util/log.c
index 1ca13059ee..c25643dc99 100644
--- a/util/log.c
+++ b/util/log.c
@@ -24,8 +24,10 @@
 #include "qapi/error.h"
 #include "qemu/cutils.h"
 #include "trace/control.h"
+#include "qemu/thread.h"
 
 static char *logfilename;
+static QemuMutex qemu_logfile_mutex;
 FILE *qemu_logfile;
 int qemu_loglevel;
 static int log_append = 0;
@@ -49,6 +51,11 @@ int qemu_log(const char *fmt, ...)
     return ret;
 }
 
+static void __attribute__((__constructor__)) qemu_logfile_init(void)
+{
+    qemu_mutex_init(&qemu_logfile_mutex);
+}
+
 static bool log_uses_own_buffers;
 
 /* enable or disable low levels log */
@@ -58,6 +65,9 @@ void qemu_set_log(int log_flags)
 #ifdef CONFIG_TRACE_LOG
     qemu_loglevel |= LOG_TRACE;
 #endif
+
+    g_assert(qemu_logfile_mutex.initialized);
+    qemu_mutex_lock(&qemu_logfile_mutex);
     if (!qemu_logfile &&
         (is_daemonized() ? logfilename != NULL : qemu_loglevel)) {
         if (logfilename) {
@@ -93,6 +103,7 @@ void qemu_set_log(int log_flags)
             log_append = 1;
         }
     }
+    qemu_mutex_unlock(&qemu_logfile_mutex);
     if (qemu_logfile &&
         (is_daemonized() ? logfilename == NULL : !qemu_loglevel)) {
         qemu_log_close();
@@ -230,12 +241,15 @@ void qemu_log_flush(void)
 /* Close the log file */
 void qemu_log_close(void)
 {
+    g_assert(qemu_logfile_mutex.initialized);
+    qemu_mutex_lock(&qemu_logfile_mutex);
     if (qemu_logfile) {
         if (qemu_logfile != stderr) {
             fclose(qemu_logfile);
         }
         qemu_logfile = NULL;
     }
+    qemu_mutex_unlock(&qemu_logfile_mutex);
 }
 
 const QEMULogItem qemu_log_items[] = {
-- 
2.17.1