commit f8e546e6090002cde90c21c83b8cdef311e50816
author Mark Salyzyn <salyzyn@google.com> Mon Nov 30 11:36:09 2015 -0800
committer Mark Salyzyn <salyzyn@google.com> Mon Dec 07 14:24:02 2015 -0800
tree 4b5fe35a78c69b0ec9294478a429ad6369df3156
parent fc9f5b8af440974fb390f4572fa526cc68d824db

liblog: Support for ANDROID_LOG_WRAP mode flag on reader

If ANDROID_LOG_WRAP is specified, add timeout=3600 to the reader
request. logd will comply by going to sleep with the socket open.
If the start time is about to wrap or get pruned in the specified log
buffers, then wakeup and dump the logs; or wakeup on timeout,
whichever comes first.

Bug: 25929746
Change-Id: I531b4317a20abcf3ba87d78c68fa2f268a4488ab

include/log/logger.h

diff --git a/include/log/logger.h b/include/log/logger.h
index ff70529..b3928a7 100644
--- a/include/log/logger.h
+++ b/include/log/logger.h
@@ -163,6 +163,8 @@
 #define ANDROID_LOG_RDWR     O_RDWR
 #define ANDROID_LOG_ACCMODE  O_ACCMODE
 #define ANDROID_LOG_NONBLOCK O_NONBLOCK
+#define ANDROID_LOG_WRAP     0x40000000 /* Block until buffer about to wrap */
+#define ANDROID_LOG_WRAP_DEFAULT_TIMEOUT 7200 /* 2 hour default */
 #define ANDROID_LOG_PSTORE   0x80000000
 
 struct logger_list *android_logger_list_alloc(int mode,

liblog/README

diff --git a/liblog/README b/liblog/README
index f29ac04..df1e68c 100644
--- a/liblog/README
+++ b/liblog/README
@@ -116,6 +116,10 @@
        code,  otherwise the  android_logger_list_read  call will block for new
        entries.
 
+       The  ANDROID_LOG_WRAP  mode flag to the  android_logger_list_alloc_time
+       signals  logd to quiesce  the reader until the buffer is about to prune
+       at the start time then proceed to dumping content.
+
        The  ANDROID_LOG_PSTORE mode flag to the android_logger_open is used to
        switch from the active logs to the persistent logs from before the last
        reboot.

liblog/log_read.c

diff --git a/liblog/log_read.c b/liblog/log_read.c
index cfc8a7a..fb86757 100644
--- a/liblog/log_read.c
+++ b/liblog/log_read.c
@@ -797,6 +797,14 @@
         }
 
         if (logger_list->start.tv_sec || logger_list->start.tv_nsec) {
+            if (logger_list->mode & ANDROID_LOG_WRAP) {
+                // ToDo: alternate API to allow timeout to be adjusted.
+                ret = snprintf(cp, remaining, " timeout=%u",
+                               ANDROID_LOG_WRAP_DEFAULT_TIMEOUT);
+                ret = min(ret, remaining);
+                remaining -= ret;
+                cp += ret;
+            }
             ret = snprintf(cp, remaining, " start=%" PRIu32 ".%09" PRIu32,
                            logger_list->start.tv_sec,
                            logger_list->start.tv_nsec);