Pin lmkd for real

We pin lmkd in memory so that we don't take page faults (and thus
requisition memory) while we're in the process of responding to a
low-memory condition. mlockall(2) is the right primitive for this
pinning. Previously, we used the MCL_FUTURE flag to mlockall: used
this way, mlockall doesn't actually pin all pages in memory, since
MCL_FUTURE affects only the default flags for future mappings and
doesn't affect mapping already in existence at the time of the
mlockall call --- like the lmkd executable itself.

This patch adds the MCL_CURRENT flag, which also pins all pages
already mapped.

Test: code inspection
Change-Id: I4563959367a2f0a9cadc3ea41731b7f311326685

1 files changed, 3 insertions, 1 deletions

diff --git a/lmkd/lmkd.c b/lmkd/lmkd.c
index 5cfa2c887..fd83ecc28 100644
--- a/lmkd/lmkd.c
+++ b/lmkd/lmkd.c
@@ -900,7 +900,9 @@ int main(int argc __unused, char **argv __unused) {
     downgrade_pressure = (int64_t)property_get_int32("ro.lmk.downgrade_pressure", 60);
     is_go_device = property_get_bool("ro.config.low_ram", false);
 
-    mlockall(MCL_FUTURE);
+    if (mlockall(MCL_CURRENT | MCL_FUTURE))
+        ALOGW("mlockall failed: errno=%d", errno);
+
     sched_setscheduler(0, SCHED_FIFO, &param);
     if (!init())
         mainloop();