[PATCH] D39624: [Sanitizers] Call NanoTime() conditionally.

[Aleksey Shlyapnikov via Phabricator via llvm-commits]

alekseyshl created this revision.
Herald added a subscriber: kubamracek.

Call NanoTime() in primary 64 bit allocator only when necessary,
otherwise the unwarranted syscall causes problems in sandbox environments.
ReleaseToOSIntervalMs() conditional allows them to turn the feature off
with allocator_release_to_os_interval_ms=-1 flag.


https://reviews.llvm.org/D39624

Files:
  lib/sanitizer_common/sanitizer_allocator_primary64.h


Index: lib/sanitizer_common/sanitizer_allocator_primary64.h
===================================================================
--- lib/sanitizer_common/sanitizer_allocator_primary64.h
+++ lib/sanitizer_common/sanitizer_allocator_primary64.h
@@ -677,7 +677,10 @@
         // preventing just allocated memory from being released sooner than
         // necessary and also preventing extraneous ReleaseMemoryPagesToOS calls
         // for short lived processes.
-        region->rtoi.last_release_at_ns = NanoTime();
+        // Do it only when the feature is turned on, to avoid a potentially
+        // extraneous syscall.
+        if (ReleaseToOSIntervalMs() >= 0)
+          region->rtoi.last_release_at_ns = NanoTime();
       }
       // Do the mmap for the user memory.
       uptr map_size = kUserMapSize;


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