[Qemu-devel] [PATCH v2] trace: Flush trace buffer on exit

[Qemu-devel] [PATCH v2] trace: Flush trace buffer on exit

[Stefan Hajnoczi]

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
This patch is against the tracing branch:

http://repo.or.cz/w/qemu/stefanha.git/shortlog/refs/heads/tracing

v2:
 * Reset trace_idx in flush_trace_buffer().

 simpletrace.c |   27 ++++++++++++++++++---------
 1 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/simpletrace.c b/simpletrace.c
index ace009f..4a4203e 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -22,6 +22,23 @@ static TraceRecord trace_buf[TRACE_BUF_LEN];
 static unsigned int trace_idx;
 static FILE *trace_fp;
 
+static void flush_trace_buffer(void)
+{
+    if (!trace_fp) {
+        trace_fp = fopen("/tmp/trace.log", "w");
+        if (trace_fp) {
+            atexit(flush_trace_buffer);
+        }
+    }
+    if (trace_fp) {
+        size_t unused; /* for when fwrite(3) is declared warn_unused_result */
+        unused = fwrite(trace_buf, trace_idx * sizeof(trace_buf[0]), 1, trace_fp);
+    }
+
+    /* Discard written trace records */
+    trace_idx = 0;
+}
+
 static void trace(TraceEventID event, unsigned long x1,
                   unsigned long x2, unsigned long x3,
                   unsigned long x4, unsigned long x5)
@@ -44,15 +61,7 @@ static void trace(TraceEventID event, unsigned long x1,
     rec->x5 = x5;
 
     if (++trace_idx == TRACE_BUF_LEN) {
-        trace_idx = 0;
-
-        if (!trace_fp) {
-            trace_fp = fopen("/tmp/trace.log", "w");
-        }
-        if (trace_fp) {
-            size_t result = fwrite(trace_buf, sizeof trace_buf, 1, trace_fp);
-            result = result;
-        }
+        flush_trace_buffer();
     }
 }
 
-- 
1.7.1