trace-cmd: Do not use threads for extract

Currently the trace-cmd extract function uses the forked threads to
read the data from the ring buffers. As this is not a live trace and
the program does not end till all the buffers are flushed to disk,
there is no need to use the threads. Just serially read each buffer
into a file and then pull them together normally.

This also fixes a bug that was triggered in the kernel where reading
the trace_pipe_raw file after EOF will yield the last page again,
causing the trace-cmd extract to produce duplicate pages.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 25 insertions, 12 deletions

diff --git a/trace-recorder.c b/trace-recorder.c
index e57ef9b..4a01fb9 100644
--- a/trace-recorder.c
+++ b/trace-recorder.c
@@ -156,10 +156,32 @@ static long splice_data(struct tracecmd_recorder *recorder)
         return ret;
 }
 
+long tracecmd_flush_recording(struct tracecmd_recorder *recorder)
+{
+        char *buf[recorder->page_size];
+        long total = 0;
+        long ret;
+
+        do {
+                ret = splice_data(recorder);
+                if (ret < 0)
+                        return ret;
+                total += ret;
+        } while (ret);
+
+        /* splice only reads full pages */
+        do {
+                ret = read(recorder->trace_fd, buf, recorder->page_size);
+                if (ret > 0)
+                        write(recorder->fd, buf, ret);
+        } while (ret > 0);
+
+        return total;
+}
+
 int tracecmd_start_recording(struct tracecmd_recorder *recorder, unsigned long sleep)
 {
         struct timespec req;
-        char *buf[recorder->page_size];
         long ret;
 
         recorder->stop = 0;
@@ -175,21 +197,12 @@ int tracecmd_start_recording(struct tracecmd_recorder *recorder, unsigned long s
                         return ret;
         } while (!recorder->stop);
 
-        /* Flush via splice first */
-        do {
-                ret = splice_data(recorder);
-        } while (ret > 0);
+        /* Flush out the rest */
+        ret = tracecmd_flush_recording(recorder);
 
         if (ret < 0)
                 return ret;
 
-        /* splice only reads full pages */
-        do {
-                ret = read(recorder->trace_fd, buf, recorder->page_size);
-                if (ret > 0)
-                        write(recorder->fd, buf, ret);
-        } while (ret > 0);
-
         return 0;
 }