Added Thread#pid. Closes #3365.

Unfortunately, this works great on Linux and not-so-great on OS X. I was
unable to find any syscall that would provide the same behavior as Linux.

We also may end up needing more #ifdefs.

Author: brixen

kernel/common/thread.rb

@@ -12,6 +12,7 @@ def self.exclusive
   end
 
   attr_reader :recursive_objects
+  attr_reader :pid
 
   # Implementation note: ideally, the recursive_objects
   # lookup table would be different per method call.

vm/builtin/thread.cpp

@@ -20,6 +20,8 @@
 #include "metrics.hpp"
 #include "util/logger.hpp"
 
+#include <sys/syscall.h>
+
 /* HACK: returns a value that should identify a native thread
  * for debugging threading issues. The winpthreads library
  * defines pthread_t to be a structure not a pointer.
@@ -73,6 +75,7 @@ namespace rubinius {
     thr->joins(state, Array::create(state, 1));
     thr->killed(state, cFalse);
     thr->priority(state, Fixnum::from(0));
+    thr->pid(state, Fixnum::from(0));
     thr->klass(state, klass);
 
     vm->thread.set(thr);
@@ -289,6 +292,12 @@ namespace rubinius {
 
     NativeMethod::init_thread(state);
 
+#ifdef __APPLE__
+    vm->thread->pid(state, Fixnum::from(syscall(SYS_thread_selfid)));
+#else
+    vm->thread->pid(state, Fixnum::from(syscall(SYS_gettid)));
+#endif
+
     // Lock the thread object and unlock it at __run__ in the ruby land.
     vm->thread->alive(state, cTrue);
     vm->thread->init_lock_.unlock();

vm/builtin/thread.hpp

@@ -47,6 +47,7 @@ namespace rubinius {
     Array* joins_; // slot
     Object* killed_; // slot
     Fixnum* priority_; // slot
+    Fixnum* pid_; // slot
 
     utilities::thread::SpinLock init_lock_;
     utilities::thread::Mutex join_lock_;
@@ -88,6 +89,7 @@ namespace rubinius {
     attr_accessor(joins, Array);
     attr_accessor(killed, Object);
     attr_accessor(priority, Fixnum);
+    attr_accessor(pid, Fixnum);
 
     VM* vm() const {
       return vm_;