[PATCH v2 3/5] trace-cmd: Add new API to merge two trace files

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

The new API
   struct tracecmd_input *tracecmd_open_merge(const char *file, const char *primary_file);
can be used to open a trace file and adjust its timestamps to the
primary_file, if both were recorded in one tracing session.
A tracecmd_input handler to the file is allocated and returned.
The timestamps of all events are adjusted according to the time synchronization data,
recorded in the file.
The API checks if the tracing session from the both files match.
In case they do not match, the timestamps are not corrected.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/trace-cmd/trace-cmd.h |  1 +
 lib/trace-cmd/trace-input.c   | 89 +++++++++++++++++++++++++++++------
 2 files changed, 76 insertions(+), 14 deletions(-)

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index 3d2d9ae1..4a68eee1 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -142,6 +142,7 @@ typedef void (*tracecmd_handle_init_func)(struct tracecmd_input *handle,
 struct tracecmd_input *tracecmd_alloc(const char *file);
 struct tracecmd_input *tracecmd_alloc_fd(int fd);
 struct tracecmd_input *tracecmd_open(const char *file);
+struct tracecmd_input *tracecmd_open_merge(const char *file, const char *primary_file);
 struct tracecmd_input *tracecmd_open_fd(int fd);
 void tracecmd_ref(struct tracecmd_input *handle);
 void tracecmd_close(struct tracecmd_input *handle);
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index 347a595f..e02cb879 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -96,8 +96,9 @@ struct guest_trace_info {
 };
 
 struct host_trace_info {
-	unsigned long long	trace_id;
+	unsigned long long	peer_trace_id;
 	bool			sync_enable;
+	struct tracecmd_input	*peer_data;
 	int			cpu_count;
 	struct ts_offset_cpu	*cpu_time_offsets;
 };
@@ -2225,10 +2226,33 @@ error:
 	return -1;
 }
 
+static void tsync_check_enable(struct tracecmd_input *handle)
+{
+	struct host_trace_info	*host = &handle->host;
+	struct guest_trace_info *guest;
+
+	host->sync_enable = false;
+
+	if (!host->peer_data || !host->peer_data->guest ||
+	    !host->cpu_count || !host->cpu_time_offsets)
+		return;
+	if (host->peer_trace_id != host->peer_data->trace_id)
+		return;
+	guest = host->peer_data->guest;
+	while (guest) {
+		if (guest->trace_id == handle->trace_id)
+			break;
+		guest = guest->next;
+	}
+	if (!guest)
+		return;
+
+	host->sync_enable = true;
+}
+
 static int tsync_offset_load(struct tracecmd_input *handle,
 			      char *buf, int buf_size, int cpus)
 {
-	struct host_trace_info *host = &handle->host;
 	int count, cpu;
 	int ret;
 	int i;
@@ -2257,8 +2281,6 @@ static int tsync_offset_load(struct tracecmd_input *handle,
 		buf += ret;
 	}
 
-	if (host->cpu_count)
-		host->sync_enable = true;
 	return 0;
 }
 
@@ -2272,6 +2294,11 @@ static void trace_tsync_offset_free(struct host_trace_info *host)
 	free(host->cpu_time_offsets);
 	host->cpu_time_offsets = NULL;
 	host->cpu_count = 0;
+
+	if (host->peer_data) {
+		tracecmd_close(host->peer_data);
+		host->peer_data = NULL;
+	}
 }
 
 static int trace_pid_map_cmp(const void *a, const void *b)
@@ -2585,8 +2612,8 @@ static int handle_options(struct tracecmd_input *handle)
 			 */
 			if (size < 12 || handle->flags & TRACECMD_FL_IGNORE_DATE)
 				break;
-			handle->host.trace_id = tep_read_number(handle->pevent,
-								buf, 8);
+			handle->host.peer_trace_id = tep_read_number(handle->pevent,
+								     buf, 8);
 			cpus = tep_read_number(handle->pevent, buf + 8, 4);
 			tsync_offset_load(handle, buf + 12, size - 12, cpus);
 			break;
@@ -2659,6 +2686,8 @@ static int handle_options(struct tracecmd_input *handle)
 
 	handle->cpustats = cpustats;
 
+	tsync_check_enable(handle);
+
 	return 0;
 }
 
@@ -3192,11 +3221,8 @@ struct tracecmd_input *tracecmd_alloc(const char *file)
 	return tracecmd_alloc_fd(fd);
 }
 
-/**
- * tracecmd_open_fd - create a tracecmd_handle from the trace.dat file descriptor
- * @fd: the file descriptor for the trace.dat file
- */
-struct tracecmd_input *tracecmd_open_fd(int fd)
+static struct tracecmd_input *tracecmd_open_fd_ext(int fd,
+						   struct tracecmd_input *merge)
 {
 	struct tracecmd_input *handle;
 	int ret;
@@ -3204,7 +3230,7 @@ struct tracecmd_input *tracecmd_open_fd(int fd)
 	handle = tracecmd_alloc_fd(fd);
 	if (!handle)
 		return NULL;
-
+	handle->host.peer_data = merge;
 	if (tracecmd_read_headers(handle) < 0)
 		goto fail;
 
@@ -3218,6 +3244,15 @@ fail:
 	return NULL;
 }
 
+/**
+ * tracecmd_open_fd - create a tracecmd_handle from the trace.dat file descriptor
+ * @fd: the file descriptor for the trace.dat file
+ */
+struct tracecmd_input *tracecmd_open_fd(int fd)
+{
+	return tracecmd_open_fd_ext(fd, NULL);
+}
+
 /**
  * tracecmd_open - create a tracecmd_handle from a given file
  * @file: the file name of the file that is of tracecmd data type.
@@ -3230,7 +3265,33 @@ struct tracecmd_input *tracecmd_open(const char *file)
 	if (fd < 0)
 		return NULL;
 
-	return tracecmd_open_fd(fd);
+	return tracecmd_open_fd_ext(fd, NULL);
+}
+
+/**
+ * tracecmd_open_merge - create a tracecmd_handle from a given file and
+ * @file: the file name of the file that is of tracecmd data type.
+ */
+struct tracecmd_input *tracecmd_open_merge(const char *file,
+					   const char *primary_file)
+{
+	struct tracecmd_input *primary = NULL;
+	int fd;
+
+	if (!primary_file)
+		return tracecmd_open(file);
+
+	fd = open(file, O_RDONLY);
+	if (fd < 0)
+		return NULL;
+
+	primary = tracecmd_open(primary_file);
+	if (!primary) {
+		close(fd);
+		return NULL;
+	}
+
+	return tracecmd_open_fd_ext(fd, primary);
 }
 
 /**
@@ -3812,7 +3873,7 @@ int tracecmd_get_guest_cpumap(struct tracecmd_input *handle,
  */
 unsigned long long tracecmd_get_tsync_peer(struct tracecmd_input *handle)
 {
-	return handle->host.trace_id;
+	return handle->host.peer_trace_id;
 }
 
 /**
-- 
2.25.1