CPU profiler: make code events handling scalable.

src/platform-linux.cc

 // Copyright 2006-2008 the V8 project authors. 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 147 matching lines @@
   return 8;
 #elif V8_TARGET_ARCH_MIPS
   return 8;
 #endif
   // With gcc 4.4 the tree vectorization optimizer can generate code
   // that requires 16 byte alignment such as movdqa on x86.
   return 16;
 }
 
 
+#ifdef V8_TARGET_ARCH_ARM
+// 0xffff0fa0 is the hard coded address of a function provided by
+// the kernel which implements a memory barrier. On older
+// ARM architecture revisions (pre-v6) this may be implemented using
+// a syscall. This address is stable, and in active use (hard coded)
+// by at least glibc-2.7 and the Android C library.
+typedef void (*LinuxKernelMemoryBarrierFunc)(void);
+LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
+    (LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
+#endif
+
+void OS::ReleaseStore(volatile AtomicWord* ptr, AtomicWord value) {
+#ifdef V8_TARGET_ARCH_ARM
+  pLinuxKernelMemoryBarrier();
+#else
+  __asm__ __volatile__("" : : : "memory");
+  // An x86 store acts as a release barrier.
+#endif
+  *ptr = value;
+}
+
+
 const char* OS::LocalTimezone(double time) {
   if (isnan(time)) return "";
   time_t tv = static_cast<time_t>(floor(time/msPerSecond));
   struct tm* t = localtime(&tv);
   if (NULL == t) return "";
   return t->tm_zone;
 }
 
 
 double OS::LocalTimeOffset() {
@@ skipping 652 matching lines @@
 
   // This sampler is no longer the active sampler.
   active_sampler_ = NULL;
   active_ = false;
 }
 
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal