logd: correct duplicate message state machine
Inspection turned up that for the case of three identical messages,
the result would be a stutter of the first message only. Added
comments to describe the state machine, incoming variables, outcoming
and false condition outputs, for proper maintenance in the future.
Test: gTest liblog-benchmarks BM_log_maximum* and manually check
for correct midstream chatty messages,
Bug: 33535908
Change-Id: I852260d18a484e6207b80063159f1a74eaa83b55
diff --git a/logd/LogBuffer.cpp b/logd/LogBuffer.cpp
index d476596..3552f70 100644
--- a/logd/LogBuffer.cpp
+++ b/logd/LogBuffer.cpp
@@ -206,6 +206,68 @@
if (currentLast) {
LogBufferElement *dropped = droppedElements[log_id];
unsigned short count = dropped ? dropped->getDropped() : 0;
+ //
+ // State Init
+ // incoming:
+ // dropped = NULL
+ // currentLast = NULL;
+ // elem = incoming message
+ // outgoing:
+ // dropped = NULL -> State 0
+ // currentLast = copy of elem
+ // log elem
+ // State 0
+ // incoming:
+ // count = 0
+ // dropped = NULL
+ // currentLast = copy of last message
+ // elem = incoming message
+ // outgoing: (if *elem == *currentLast)
+ // dropped = copy of first identical message -> State 1
+ // currentLast = reference to elem
+ // break: (if *elem != *currentLast)
+ // dropped = NULL -> State 0
+ // delete copy of last message (incoming currentLast)
+ // currentLast = copy of elem
+ // log elem
+ // State 1
+ // incoming:
+ // count = 0
+ // dropped = copy of first identical message
+ // currentLast = reference to last held-back incoming
+ // message
+ // elem = incoming message
+ // outgoing: (if *elem == *currentLast)
+ // delete copy of first identical message (dropped)
+ // dropped = reference to last held-back incoming
+ // message set to chatty count of 1 -> State 2
+ // currentLast = reference to elem
+ // break:
+ // delete dropped
+ // dropped = NULL -> State 0
+ // log reference to last held-back (currentLast)
+ // currentLast = copy of elem
+ // log elem
+ // State 2
+ // incoming:
+ // count = chatty count
+ // dropped = chatty message holding count
+ // currentLast = reference to last held-back incoming
+ // message.
+ // dropped = chatty message holding count
+ // elem = incoming message
+ // outgoing: (if *elem == *currentLast)
+ // delete chatty message holding count
+ // dropped = reference to last held-back incoming
+ // message, set to chatty count + 1
+ // currentLast = reference to elem
+ // break:
+ // log dropped (chatty message)
+ // dropped = NULL -> State 0
+ // log reference to last held-back (currentLast)
+ // currentLast = copy of elem
+ // log elem
+ //
if (identical(elem, currentLast)) {
if (dropped) {
if (count == USHRT_MAX) {
@@ -226,13 +288,15 @@
pthread_mutex_unlock(&mLogElementsLock);
return len;
}
- if (dropped) {
- log(dropped);
+ if (dropped) { // State 1 or 2
+ if (count) { // State 2
+ log(dropped); // report chatty
+ } else { // State 1
+ delete dropped;
+ }
droppedElements[log_id] = NULL;
- }
- if (count) {
- log(currentLast);
- } else {
+ log(currentLast); // report last message in the series
+ } else { // State 0
delete currentLast;
}
}