trace-cmd: Add locked attribute to record and debug peek freeing

Add a "locked" attribute to the record structure. This will be
set when a peek is returned and cleared on read. This will help
debug cases that incorrectly free a record returned by peek.

The internal helper function free_next() is added to do the freeing
of the next record used by peek.

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

2 files changed, 36 insertions, 25 deletions

diff --git a/parse-events.h b/parse-events.h
index e6ea2ab..66e0eb5 100644
--- a/parse-events.h
+++ b/parse-events.h
@@ -21,6 +21,7 @@ struct record {
         int                     size;           /* size of data */
         void                    *data;
         int                     cpu;
+        int                     locked;         /* Do not allow freeing */
         void                    *private;
 };
 
diff --git a/trace-input.c b/trace-input.c
index 306b7a5..8c2a738 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -622,11 +622,8 @@ static void free_page(struct tracecmd_input *handle, int cpu)
         handle->cpu_data[cpu].page = NULL;
 }
 
-void free_record(struct record *record)
+static void __free_record(struct record *record)
 {
-        if (!record)
-                return;
-
         if (record->private) {
                 struct page *page = record->private;
                 __free_page(page->handle, page);
@@ -635,6 +632,29 @@ void free_record(struct record *record)
         free(record);
 }
 
+void free_record(struct record *record)
+{
+        if (!record)
+                return;
+
+        if (record->locked)
+                die("freeing record when it is locked!");
+        record->data = NULL;
+
+        __free_record(record);
+}
+
+static void free_next(struct tracecmd_input *handle, int cpu)
+{
+        struct record *record = handle->cpu_data[cpu].next;
+
+        if (!record)
+                return;
+
+        handle->cpu_data[cpu].next = NULL;
+        __free_record(record);
+}
+
 /*
  * Page is mapped, now read in the page header info.
  */
@@ -833,10 +853,7 @@ peek_event(struct tracecmd_input *handle, unsigned long long offset,
          * tracecmd_read_at.
          */
         update_page_info(handle, cpu);
-        if (handle->cpu_data[cpu].next) {
-                free_record(handle->cpu_data[cpu].next);
-                handle->cpu_data[cpu].next = NULL;
-        }
+        free_next(handle, cpu);
 
         do {
                 free_record(record);
@@ -1016,10 +1033,7 @@ tracecmd_read_cpu_first(struct tracecmd_input *handle, int cpu)
                 return NULL;
 
         handle->cpu_data[cpu].index = 0;
-        if (handle->cpu_data[cpu].next) {
-                free_record(handle->cpu_data[cpu].next);
-                handle->cpu_data[cpu].next = NULL;
-        }
+        free_next(handle, cpu);
 
         return tracecmd_read_data(handle, cpu);
 }
@@ -1415,6 +1429,8 @@ tracecmd_peek_data(struct tracecmd_input *handle, int cpu)
         if (handle->cpu_data[cpu].next) {
 
                 record = handle->cpu_data[cpu].next;
+                if (!record->data)
+                        die("Something freed the record");
 
                 if (handle->cpu_data[cpu].timestamp == record->ts)
                         return record;
@@ -1423,7 +1439,7 @@ tracecmd_peek_data(struct tracecmd_input *handle, int cpu)
                  * The timestamp changed, which means the cached
                  * record is no longer valid. Reread a new record.
                  */
-                free_record(record);
+                free_next(handle, cpu);
         }
 
         if (!page)
@@ -1495,6 +1511,7 @@ read_again:
 
         record->record_size = handle->cpu_data[cpu].index - index;
         record->private = page;
+        record->locked = 1;
         page->ref_count++;
 
         return record;
@@ -1517,6 +1534,8 @@ tracecmd_read_data(struct tracecmd_input *handle, int cpu)
 
         record = tracecmd_peek_data(handle, cpu);
         handle->cpu_data[cpu].next = NULL;
+        if (record)
+                record->locked = 0;
 
         return record;
 }
@@ -1606,10 +1625,7 @@ tracecmd_read_prev(struct tracecmd_input *handle, struct record *record)
         index = offset - page_offset;
 
         /* Note, the record passed in could have been a peek */
-        if (cpu_data->next) {
-                free_record(cpu_data->next);
-                cpu_data->next = NULL;
-        }
+        free_next(handle, cpu);
 
         /* Reset the cursor */
         /* Should not happen */
@@ -1975,14 +1991,8 @@ void tracecmd_close(struct tracecmd_input *handle)
                 return;
 
         for (cpu = 0; cpu < handle->cpus; cpu++) {
-                struct record *rec;
-                /*
-                 * The tracecmd_peek_data may have cached a record
-                 * Do a read to flush it out.
-                 */
-                rec = tracecmd_read_data(handle, cpu);
-                if (rec)
-                        free_record(rec);
+                /* The tracecmd_peek_data may have cached a record */
+                free_next(handle, cpu);
                 free_page(handle, cpu);
                 if (!list_empty(&handle->cpu_data[cpu].pages))
                         warning("pages still allocated on cpu %d", cpu);