Merge google-perftools r109 (the current contents of third_party/tcmalloc/vendor)

third_party/tcmalloc/chromium/src/base/spinlock_linux-inl.h

 /* Copyright (c) 2009, Google Inc.
  * All rights reserved.
  * 
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  * 
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 10 matching lines @@
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * ---
- * This file is a Linux-specific part of spinlock.cc
+ * This file is a Linux-specific part of spinlock_internal.cc
  */
 
 #include <sched.h>
 #include <time.h>
+#include <limits.h>
+#include "base/linux_syscall_support.h"
 
 #define FUTEX_WAIT 0
 #define FUTEX_WAKE 1
 #define FUTEX_PRIVATE_FLAG 128
 
 // Note: Instead of making direct system calls that are inlined, we rely
 //       on the syscall() function in glibc to do the right thing. This
 //       is necessary to make the code compatible with the seccomp sandbox,
 //       which needs to be able to find and patch all places where system
 //       calls are made. Scanning through and patching glibc is fast, but
 //       doing so on the entire Chrome binary would be prohibitively
 //       expensive.
 //       This is a notable change from the upstream version of tcmalloc,
 //       which prefers direct system calls in order to improve compatibility
 //       with older toolchains and runtime libraries.
 
 static bool have_futex;
 static int futex_private_flag = FUTEX_PRIVATE_FLAG;
 
 namespace {
 static struct InitModule {
   InitModule() {
     int x = 0;
     // futexes are ints, so we can use them only when
     // that's the same size as the lockword_ in SpinLock.
+#ifdef __arm__
+    // ARM linux doesn't support sys_futex1(void*, int, int, struct timespec*);
+    have_futex = 0;
+#else
     have_futex = (sizeof (Atomic32) == sizeof (int) && 
                   syscall(__NR_futex, &x, FUTEX_WAKE, 1, 0) >= 0);
+#endif
     if (have_futex &&
         syscall(__NR_futex, &x, FUTEX_WAKE | futex_private_flag, 1, 0) < 0) {
       futex_private_flag = 0;
     }
   }
 } init_module;
+
 }  // anonymous namespace
 
-static void SpinLockWait(volatile Atomic32 *w) {
-  int save_errno = errno;
-  struct timespec tm;
-  tm.tv_sec = 0;
-  if (have_futex) {
-    int value;
-    tm.tv_nsec = 1000000;   // 1ms; really we're trying to sleep for one kernel
-                            // clock tick
-    while ((value = base::subtle::Acquire_CompareAndSwap(w, 0, 1)) != 0) {
+
+namespace base {
+namespace internal {
+
+void SpinLockDelay(volatile Atomic32 *w, int32 value, int loop) {
+  if (loop != 0) {
+    int save_errno = errno;
+    struct timespec tm;
+    tm.tv_sec = 0;
+    if (have_futex) {
+      tm.tv_nsec = 1000000;   // 1ms; really we're trying to sleep for one
+                              // kernel clock tick
+    } else {
+      tm.tv_nsec = 2000001;   // above 2ms so linux 2.4 doesn't spin
+    }
+    if (have_futex) {
       syscall(__NR_futex, reinterpret_cast<int *>(const_cast<Atomic32 *>(w)),
-          FUTEX_WAIT | futex_private_flag,
-          value, reinterpret_cast<struct kernel_timespec *>(&tm));
-    }
-  } else {
-    tm.tv_nsec = 2000001;       // above 2ms so linux 2.4 doesn't spin
-    if (base::subtle::NoBarrier_Load(w) != 0) {
-      sched_yield();
-    }
-    while (base::subtle::Acquire_CompareAndSwap(w, 0, 1) != 0) {
+                FUTEX_WAIT | futex_private_flag,
+                value, reinterpret_cast<struct kernel_timespec *>(&tm));
+    } else {
       nanosleep(&tm, NULL);
     }
+    errno = save_errno;
   }
-  errno = save_errno;
 }
 
-static void SpinLockWake(volatile Atomic32 *w) {
+void SpinLockWake(volatile Atomic32 *w, bool all) {
   if (have_futex) {
     syscall(__NR_futex, reinterpret_cast<int *>(const_cast<Atomic32 *>(w)),
               FUTEX_WAKE | futex_private_flag, 1, 0);
   }
 }
+
+} // namespace internal
+} // namespace base