Make TurnSequencer non-x86-safe

Summary: `TurnSequencer` uses inline assembly, which obviously won't work on ARM. Guard said assembly to x86{,_64} targets. Test Plan: Added an always-false `static_assert` to the `ifdef` block, confirmed it gets triggered (i.e., we're not removing the `pause` on x86_64). Reviewed By: [email protected] Subscribers: folly-diffs@, yfeldblum, chalfant FB internal diff: D2069320 Signature: t1:2069320:1431663264:3b3fb4282cf2b755f9b26c76b608b91ff665e226
dwlinux · Jun 3, 2015 · 8b9a09c · 8b9a09c
1 parent 7a4c781
commit 8b9a09c
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/folly/detail/TurnSequencer.h b/folly/detail/TurnSequencer.h
@@ -22,6 +22,7 @@
 #include <unistd.h>
 
 #include <folly/detail/Futex.h>
+#include <folly/Portability.h>
 
 namespace folly {
 
@@ -123,7 +124,9 @@ struct TurnSequencer {
       // the first effectSpinCutoff tries are spins, after that we will
       // record ourself as a waiter and block with futexWait
       if (tries < effectiveSpinCutoff) {
+#if defined(__i386__) || FOLLY_X64
         asm volatile ("pause");
+#endif
         continue;
       }