commit 2ca167ef95f17314d7108372da3a9616c758a838
author Mark Salyzyn <salyzyn@google.com> Thu Apr 13 08:19:52 2017 -0700
committer Mark Salyzyn <salyzyn@google.com> Thu Apr 13 13:16:59 2017 -0700
tree ab2c8fdb9d1c08a688ae35bfc484912b2ad467e1
parent ffc5957f1185aa54e9bea7f4c3942dc20c107916

liblog: android_log_event_list class permit -EBUSY retry

write() method was one-shot, a second shot on -EBUSY would always
return -EBUSY even if successful.  Reset internal error if -EBUSY
when retransmitting.  write() now reports a positive count for
transmission success.  Composition errors trump transmission errors.

Test: gTest logcat-unit-tests --gtest_filter=*.descriptive while
      under heavy DOS stress levels of logging.
Bug: 31456426
Change-Id: Ib1920c3f10cf1df8ad8eb6a884724794b577b29d

liblog/include/log/log_event_list.h

diff --git a/liblog/include/log/log_event_list.h b/liblog/include/log/log_event_list.h
index 55953fc..057be5d 100644
--- a/liblog/include/log/log_event_list.h
+++ b/liblog/include/log/log_event_list.h
@@ -17,6 +17,7 @@
 #ifndef _LIBS_LOG_EVENT_LIST_H
 #define _LIBS_LOG_EVENT_LIST_H
 
+#include <errno.h>
 #include <stdint.h>
 
 #if (defined(__cplusplus) && defined(_USING_LIBCXX))
@@ -148,6 +149,7 @@
     return ctx;
   }
 
+  /* return errors or transmit status */
   int status() const {
     return ret;
   }
@@ -209,14 +211,16 @@
   }
 
   int write(log_id_t id = LOG_ID_EVENTS) {
+    /* facilitate -EBUSY retry */
+    if ((ret == -EBUSY) || (ret > 0)) ret = 0;
     int retval = android_log_write_list(ctx, id);
-    if (retval < 0) ret = retval;
+    /* existing errors trump transmission errors */
+    if (!ret) ret = retval;
     return ret;
   }
 
   int operator<<(log_id_t id) {
-    int retval = android_log_write_list(ctx, id);
-    if (retval < 0) ret = retval;
+    write(id);
     android_log_destroy(&ctx);
     return ret;
   }