trace-cmd: Add reference counter to tracecmd_input

Because different parts of an application may reference a tracecmd_input
handle, add a reference counter to make it easier to know when to free
the handle.

All parts of an application that allocate or calls tracecmd_ref on the
handle must now call tracecmd_close on it too.

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

2 files changed, 34 insertions, 0 deletions

diff --git a/trace-cmd.h b/trace-cmd.h
index 18d615c..c468cf7 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -45,6 +45,7 @@ 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_fd(int fd);
+void tracecmd_ref(struct tracecmd_input *handle);
 void tracecmd_close(struct tracecmd_input *handle);
 int tracecmd_read_headers(struct tracecmd_input *handle);
 int tracecmd_long_size(struct tracecmd_input *handle);
diff --git a/trace-input.c b/trace-input.c
index 13896eb..d123c0d 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -52,6 +52,7 @@ struct tracecmd_input {
         int                     page_size;
         int                     read_page;
         int                     cpus;
+        int                     ref;
         struct cpu_data         *cpu_data;
 
         /* file information */
@@ -1496,6 +1497,7 @@ struct tracecmd_input *tracecmd_alloc_fd(int fd)
         memset(handle, 0, sizeof(*handle));
 
         handle->fd = fd;
+        handle->ref = 1;
 
         if (do_read_check(handle, buf, 3))
                 goto failed_read;
@@ -1605,6 +1607,29 @@ struct tracecmd_input *tracecmd_open(const char *file)
         return tracecmd_open_fd(fd);
 }
 
+/**
+ * tracecmd_ref - add a reference to the handle
+ * @handle: input handle for the trace.dat file
+ *
+ * Some applications may share a handle between parts of
+ * the application. Let those parts add reference counters
+ * to the handle, and the last one to close it will free it.
+ */
+void tracecmd_ref(struct tracecmd_input *handle)
+{
+        if (!handle)
+                return;
+
+        handle->ref++;
+}
+
+/**
+ * tracecmd_close - close and free the trace.dat handle
+ * @handle: input handle for the trace.dat file
+ *
+ * Close the file descriptor of the handle and frees
+ * the resources allocated by the handle.
+ */
 void tracecmd_close(struct tracecmd_input *handle)
 {
         int cpu;
@@ -1612,6 +1637,14 @@ void tracecmd_close(struct tracecmd_input *handle)
         if (!handle)
                 return;
 
+        if (handle->ref <= 0) {
+                warning("tracecmd: bad ref count on handle\n");
+                return;
+        }
+
+        if (--handle->ref)
+                return;
+
         for (cpu = 0; cpu < handle->cpus; cpu++) {
                 struct record *rec;
                 /*