Make some AsyncTest methods virtual to allow mocking them using gtest/gmock

[folly.git] / folly / PicoSpinLock.h

diff --git a/folly/PicoSpinLock.h b/folly/PicoSpinLock.h
index ce87d13eddd6a1db764f0195091e6616533a3d6b..02d7bc924183f8f5d59facaff3062731ba821504 100644 (file)
--- a/folly/PicoSpinLock.h
+++ b/folly/PicoSpinLock.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,7 +14,24 @@
  * limitations under the License.
  */
 
+/*
+ * N.B. You most likely do _not_ want to use PicoSpinLock or any other
+ * kind of spinlock.  Consider MicroLock 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
+#define FOLLY_PICO_SPIN_LOCK_H_
 
 /*
  * @author Keith Adams <kma@fb.com>
@@ -22,16 +39,16 @@
  */
 
 #include <array>
+#include <atomic>
 #include <cinttypes>
-#include <type_traits>
 #include <cstdlib>
-#include <pthread.h>
+#include <folly/Portability.h>
 #include <mutex>
-#include <atomic>
+#include <pthread.h>
+#include <type_traits>
 
 #include <glog/logging.h>
 #include <folly/detail/Sleeper.h>
-#include <folly/Portability.h>
 
 #if !FOLLY_X64 && !FOLLY_A64 && !FOLLY_PPC64
 # error "PicoSpinLock.h is currently x64, aarch64 and ppc64 only."
@@ -77,7 +94,7 @@ struct PicoSpinLock {
    */
   void init(IntType initialValue = 0) {
     CHECK(!(initialValue & kLockBitMask_));
-    lock_ = initialValue;
+    lock_ = UIntType(initialValue);
   }
 
   /*
@@ -101,7 +118,7 @@ struct PicoSpinLock {
    */
   void setData(IntType w) {
     CHECK(!(w & kLockBitMask_));
-    lock_ = (lock_ & kLockBitMask_) | w;
+    lock_ = UIntType((lock_ & kLockBitMask_) | w);
   }
 
   /*
@@ -111,7 +128,21 @@ struct PicoSpinLock {
   bool try_lock() const {
     bool ret = false;
 
-#if FOLLY_X64
+#ifdef _MSC_VER
+    switch (sizeof(IntType)) {
+      case 2:
+        // There is no _interlockedbittestandset16 for some reason :(
+        ret = _InterlockedOr16(
+            (volatile short*)&lock_, (short)kLockBitMask_) & kLockBitMask_;
+        break;
+      case 4:
+        ret = _interlockedbittestandset((volatile long*)&lock_, Bit);
+        break;
+      case 8:
+        ret = _interlockedbittestandset64((volatile long long*)&lock_, Bit);
+        break;
+    }
+#elif FOLLY_X64
 #define FB_DOBTS(size)                                  \
   asm volatile("lock; bts" #size " %1, (%2); setnc %0"  \
                : "=r" (ret)                             \
@@ -176,7 +207,20 @@ struct PicoSpinLock {
    * integer.
    */
   void unlock() const {
-#if FOLLY_X64
+#ifdef _MSC_VER
+    switch (sizeof(IntType)) {
+      case 2:
+        // There is no _interlockedbittestandreset16 for some reason :(
+        _InterlockedAnd16((volatile short*)&lock_, (short)~kLockBitMask_);
+        break;
+      case 4:
+        _interlockedbittestandreset((volatile long*)&lock_, Bit);
+        break;
+      case 8:
+        _interlockedbittestandreset64((volatile long long*)&lock_, Bit);
+        break;
+    }
+#elif FOLLY_X64
 #define FB_DOBTR(size)                          \
   asm volatile("lock; btr" #size " %0, (%1)"    \
                :                                \