[ltt-dev] [PATCH] Fix bug in lttv from 0.12.0 to 0.12.10

[Mathieu Desnoyers]

Hi,

I found a nasty event id / timetamping bug in lttv. Basically, when
enough events were registered in a channel to come up to IDs 29, 30 and
31, there were side-effects on how the timestamp update was done for the
specific event because the event id was overwritten by the case 29: in
the switch() before the test done later in a if() statement. LTTV
0.12.11 fixes this. For reference, here is the diff.

Mathieu, getting back to timestamp-sanity land.

Index: tracefile.c
===================================================================
--- tracefile.c	(revision 3321)
+++ tracefile.c	(working copy)
@@ -1256,6 +1256,7 @@
   void * pos;
   LttEvent *event;
   void *pos_aligned;
+  guint16 packed_evid;	/* event id reader from the 5 bits in header */
  
   event = &tf->event;
   pos = tf->buffer.head + event->offset;
@@ -1267,11 +1268,11 @@
   pos_aligned = pos;
   
   event->timestamp = ltt_get_uint32(LTT_GET_BO(tf), pos);
-  event->event_id = event->timestamp >> tf->tscbits;
+  event->event_id = packed_evid = event->timestamp >> tf->tscbits;
   event->timestamp = event->timestamp & tf->tsc_mask;
   pos += sizeof(guint32);
 
-  switch (event->event_id) {
+  switch (packed_evid) {
   case 29:  /* LTT_RFLAG_ID_SIZE_TSC */
     event->event_id = ltt_get_uint16(LTT_GET_BO(tf), pos);
     pos += sizeof(guint16);
@@ -1305,7 +1306,7 @@
     break;
   }
 
-  if (likely(event->event_id != 29)) {
+  if (likely(packed_evid != 29)) {
       /* No extended timestamp */
       if (event->timestamp < (tf->buffer.tsc & tf->tsc_mask))
         tf->buffer.tsc = ((tf->buffer.tsc & ~tf->tsc_mask)  /* overflow */


-- 
Mathieu Desnoyers
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