init: set oom_adj early before fork vendor_init

right now vendor_init is forked before we set oom_adj for init which
leaves a chance vendor_init could be killed in heavy memory pressure.

this CL set the oom_adj before forking everything to ensure all native
have correct oom_adj settings.

Fixes: 130824864
Test: procrank -o
Change-Id: I8af129076c3efa29f7b781459449f8f2dc853c98

init/init.cpp

@@ -625,6 +625,11 @@ int SecondStageMain(int argc, char** argv) {
     InitKernelLogging(argv, InitAborter);
     LOG(INFO) << "init second stage started!";
 
+    // Set init and its forked children's oom_adj.
+    if (auto result = WriteFile("/proc/1/oom_score_adj", "-1000"); !result) {
+        LOG(ERROR) << "Unable to write -1000 to /proc/1/oom_score_adj: " << result.error();
+    }
+
     // Enable seccomp if global boot option was passed (otherwise it is enabled in zygote).
     GlobalSeccomp();
 

rootdir/init.rc

@@ -13,9 +13,6 @@ import /init.${ro.zygote}.rc
 
 # Cgroups are mounted right before early-init using list from /etc/cgroups.json
 on early-init
-    # Set init and its forked children's oom_adj.
-    write /proc/1/oom_score_adj -1000
-
     # Disable sysrq from keyboard
     write /proc/sys/kernel/sysrq 0