Disable the signal stack on Windows

[folly.git] / folly / SpinLock.h

diff --git a/folly/SpinLock.h b/folly/SpinLock.h
index 0acbca899952813d816aa50bc7900a1145c402dd..6d10df4ad4e032aab207d52068a5ffbd9bc59a08 100644 (file)
--- a/folly/SpinLock.h
+++ b/folly/SpinLock.h
@@ -14,6 +14,22 @@
  * limitations under the License.
  */
 
+/*
+ * N.B. You most likely do _not_ want to use SpinLock or any other
+ * kind of spinlock.  Use std::mutex instead.
+ *
+ * In short, spinlocks in preemptive multi-tasking operating systems
+ * have serious problems and fast mutexes like std::mutex are almost
+ * certainly the better choice, because letting the OS scheduler put a
+ * thread to sleep is better for system responsiveness and throughput
+ * than wasting a timeslice repeatedly querying a lock held by a
+ * thread that's blocked, and you can't prevent userspace
+ * programs blocking.
+ *
+ * Spinlocks in an operating system kernel make much more sense than
+ * they do in userspace.
+ */
+
 #pragma once
 
 #include <folly/detail/SpinLockImpl.h>