trace: split trace_init_file out of trace_init_backends

This is cleaner, and improves error reporting with -daemonize.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-id: 1452174932-28657-4-git-send-email-den@openvz.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

4 files changed, 28 insertions, 12 deletions

diff --git a/trace/control.c b/trace/control.c
index 931d64c0c8..f5a497a391 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -145,17 +145,24 @@ void trace_init_events(const char *fname)
     loc_pop(&loc);
 }
 
-bool trace_init_backends(const char *file)
+void trace_init_file(const char *file)
 {
 #ifdef CONFIG_TRACE_SIMPLE
-    if (!st_init(file)) {
-        fprintf(stderr, "failed to initialize simple tracing backend.\n");
-        return false;
-    }
+    st_set_trace_file(file);
 #else
     if (file) {
         fprintf(stderr, "error: -trace file=...: "
                 "option not supported by the selected tracing backends\n");
+        exit(1);
+    }
+#endif
+}
+
+bool trace_init_backends(void)
+{
+#ifdef CONFIG_TRACE_SIMPLE
+    if (!st_init()) {
+        fprintf(stderr, "failed to initialize simple tracing backend.\n");
         return false;
     }
 #endif
diff --git a/trace/control.h b/trace/control.h
index 7905917213..d50f3996c7 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -157,7 +157,7 @@ static void trace_event_set_state_dynamic(TraceEvent *ev, bool state);
  *
  * Returns: Whether the backends could be successfully initialized.
  */
-bool trace_init_backends(const char *file);
+bool trace_init_backends(void);
 
 /**
  * trace_init_events:
@@ -170,6 +170,17 @@ bool trace_init_backends(const char *file);
  */
 void trace_init_events(const char *file);
 
+/**
+ * trace_init_file:
+ * @file:   Name of trace output file; may be NULL.
+ *          Corresponds to commandline option "-trace file=...".
+ *
+ * Record the name of the output file for the tracing backend.
+ * Exits if no selected backend does not support specifying the
+ * output file, and a non-NULL file was passed.
+ */
+void trace_init_file(const char *file);
+
 
 #include "trace/control-internal.h"
 
diff --git a/trace/simple.c b/trace/simple.c
index 56a624cac8..e8594cd00d 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -322,7 +322,7 @@ void st_set_trace_file_enabled(bool enable)
  * @file        The trace file name or NULL for the default name-<pid> set at
  *              config time
  */
-bool st_set_trace_file(const char *file)
+void st_set_trace_file(const char *file)
 {
     st_set_trace_file_enabled(false);
 
@@ -336,7 +336,6 @@ bool st_set_trace_file(const char *file)
     }
 
     st_set_trace_file_enabled(true);
-    return true;
 }
 
 void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
@@ -374,7 +373,7 @@ static GThread *trace_thread_create(GThreadFunc fn)
     return thread;
 }
 
-bool st_init(const char *file)
+bool st_init(void)
 {
     GThread *thread;
 
@@ -387,6 +386,5 @@ bool st_init(const char *file)
     }
 
     atexit(st_flush_trace_buffer);
-    st_set_trace_file(file);
     return true;
 }
diff --git a/trace/simple.h b/trace/simple.h
index 6997996855..8d1a32eba0 100644
--- a/trace/simple.h
+++ b/trace/simple.h
@@ -20,8 +20,8 @@
 
 void st_print_trace_file_status(FILE *stream, fprintf_function stream_printf);
 void st_set_trace_file_enabled(bool enable);
-bool st_set_trace_file(const char *file);
-bool st_init(const char *file);
+void st_set_trace_file(const char *file);
+bool st_init(void);
 void st_flush_trace_buffer(void);
 
 typedef struct {