logd: cap how far back in-place sort will go to 5 seconds

Add some deterministic behavior should the user change the hour
backwards when altering the device time, prevent sort-in-place
and cause the logger to land the new entries at the end.

Do not limit how far kernel logs can be sorted.

Test: gTest liblog-unit-tests logd-unit-tests logcat-unit-tests
Bug: 35373582
Change-Id: Ie897c40b97adf1e3996687a0e28c1199c41e0d0c

1 files changed, 7 insertions, 1 deletions

diff --git a/logd/LogBuffer.cpp b/logd/LogBuffer.cpp
index 1b79e89b9..352fc187f 100644
--- a/logd/LogBuffer.cpp
+++ b/logd/LogBuffer.cpp
@@ -370,13 +370,19 @@ int LogBuffer::log(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid,
 
 // assumes mLogElementsLock held, owns elem, will look after garbage collection
 void LogBuffer::log(LogBufferElement* elem) {
+    // cap on how far back we will sort in-place, otherwise append
+    static uint32_t too_far_back = 5;  // five seconds
     // Insert elements in time sorted order if possible
     //  NB: if end is region locked, place element at end of list
     LogBufferElementCollection::iterator it = mLogElements.end();
     LogBufferElementCollection::iterator last = it;
     if (__predict_true(it != mLogElements.begin())) --it;
     if (__predict_false(it == mLogElements.begin()) ||
-        __predict_true((*it)->getRealTime() <= elem->getRealTime())) {
+        __predict_true((*it)->getRealTime() <= elem->getRealTime()) ||
+        __predict_false((((*it)->getRealTime().tv_sec - too_far_back) >
+                         elem->getRealTime().tv_sec) &&
+                        (elem->getLogId() != LOG_ID_KERNEL) &&
+                        ((*it)->getLogId() != LOG_ID_KERNEL))) {
         mLogElements.push_back(elem);
     } else {
         log_time end = log_time::EPOCH;