Merge pull request #212 from dtolnay/relaxed

Change Backtrace::enabled atomic from SeqCst to Relaxed

Author: dtolnay

Diff for: src/backtrace.rs

@@ -182,7 +182,7 @@ mod capture {
     impl Backtrace {
         fn enabled() -> bool {
             static ENABLED: AtomicUsize = AtomicUsize::new(0);
-            match ENABLED.load(Ordering::SeqCst) {
+            match ENABLED.load(Ordering::Relaxed) {
                 0 => {}
                 1 => return false,
                 _ => return true,
@@ -194,7 +194,7 @@ mod capture {
                     None => false,
                 },
             };
-            ENABLED.store(enabled as usize + 1, Ordering::SeqCst);
+            ENABLED.store(enabled as usize + 1, Ordering::Relaxed);
             enabled
         }