RRO: Synchronize access to overlays.list
idmap --scan is executed as a part of the pre-loading in ZygoteInit.
The pre loading is executed in parallel for each supported architecture
(32/64 bit). This will cause a race condition in the creation of the
overlays.list file and the idmap files for the system overlays.
Apply flock on overlays.list to prevent the file from being thrown away
and recreated when it is in use by another Zygote.
Cherry-picked from AOSP.
Bug: 28032298
Test: manual
Change-Id: I51d39f121d207b11181340b68b164b60020f0c61
diff --git a/libs/androidfw/AssetManager.cpp b/libs/androidfw/AssetManager.cpp
index 8ea25d6..07044d0 100644
--- a/libs/androidfw/AssetManager.cpp
+++ b/libs/androidfw/AssetManager.cpp
@@ -35,6 +35,9 @@
#include <utils/threads.h>
#include <utils/Timers.h>
#include <utils/Trace.h>
+#ifndef _WIN32
+#include <sys/file.h>
+#endif
#include <assert.h>
#include <dirent.h>
@@ -767,6 +770,12 @@
return;
}
+#ifndef _WIN32
+ if (TEMP_FAILURE_RETRY(flock(fileno(fin), LOCK_SH)) != 0) {
+ fclose(fin);
+ return;
+ }
+#endif
char buf[1024];
while (fgets(buf, sizeof(buf), fin)) {
// format of each line:
@@ -797,6 +806,10 @@
const_cast<AssetManager*>(this)->mZipSet.addOverlay(targetPackagePath, oap);
}
}
+
+#ifndef _WIN32
+ TEMP_FAILURE_RETRY(flock(fileno(fin), LOCK_UN));
+#endif
fclose(fin);
}