commit 3c501b50b41086cde59a6811f4aa5cd3e736f5f2
author Mark Salyzyn <salyzyn@google.com> Tue Apr 18 14:09:45 2017 -0700
committer Mark Salyzyn <salyzyn@google.com> Thu Apr 20 08:24:38 2017 -0700
tree f965acd1a431bce77613286cd9a6dd33ed1190a3
parent e32517d7739f32014695d3082da50ab0186460c3

logd: reader/writer element locks

Switch to a reader writer lock for the Element List lock.  Also setup
for a reader writer lock for the Times list, but continue to use a
mutex where rdlock() and wrlock() are the same implementation for now.

This should improve general reader performance and prevent blocking of
other reader operations or exit by a single hung logd.reader.per
thread.  For example, a full length logcat of an empty buffer (eg:
crash log buffer) will hold a lock while the iterator scans the entire
list.

Test: gTest liblog-unit-tests, logd-unit-tests, logcat-unit-tests
Bug: 37378309
Bug: 37483775
Change-Id: If5723ff4a978e17d828a75321e8f0ba91d4a09e0

logd/LogTimes.h

diff --git a/logd/LogTimes.h b/logd/LogTimes.h
index ec8252e..9ca2aea 100644
--- a/logd/LogTimes.h
+++ b/logd/LogTimes.h
@@ -61,7 +61,10 @@
     const log_time mEnd;  // only relevant if mNonBlock
 
     // Protect List manipulations
-    static void lock(void) {
+    static void wrlock(void) {
+        pthread_mutex_lock(&timesLock);
+    }
+    static void rdlock(void) {
         pthread_mutex_lock(&timesLock);
     }
     static void unlock(void) {
@@ -104,7 +107,7 @@
         mError = true;
     }
     void error(void) {
-        lock();
+        wrlock();
         error_Locked();
         unlock();
     }