vm: sample pc on windows

vm/factor.cpp

@@ -212,9 +212,10 @@ void factor_vm::start_standalone_factor(int argc, vm_char **argv)
 
 factor_vm *new_factor_vm()
 {
-	factor_vm *newvm = new factor_vm();
+	THREADHANDLE thread = thread_id();
+	factor_vm *newvm = new factor_vm(thread);
 	register_vm_with_thread(newvm);
-	thread_vms[thread_id()] = newvm;
+	thread_vms[thread] = newvm;
 
 	return newvm;
 }

vm/os-windows.cpp

@@ -320,13 +320,28 @@ void factor_vm::sampler_thread_loop()
 		assert(ok);
 		new_counter.QuadPart *= samples_per_second;
 		cell samples = 0;
-		while (new_counter.QuadPart - counter.QuadPart > units_per_second.QuadPart) {
-			// We would have to suspend the thread to sample the PC
+		while (new_counter.QuadPart - counter.QuadPart > units_per_second.QuadPart)
+		{
 			++samples;
 			counter.QuadPart += units_per_second.QuadPart;
 		}
+
 		if (samples > 0)
-			enqueue_safepoint_sample(samples, 0, false);
+		{
+			DWORD suscount = SuspendThread(thread);
+			assert(suscount == 0);
+
+			CONTEXT context;
+			memset((void*)&context, 0, sizeof(CONTEXT));
+			context.ContextFlags = CONTEXT_CONTROL;
+			BOOL context_ok = GetThreadContext(thread, &context);
+			assert(context_ok);
+
+			suscount = ResumeThread(thread);
+			assert(suscount == 1);
+
+			enqueue_safepoint_sample(samples, context.EIP, false);
+		}
 	}
 }
 

vm/sampling_profiler.cpp

@@ -164,7 +164,7 @@ void factor_vm::enqueue_safepoint_sample(cell samples, cell pc, bool foreign_thr
 				atomic::add(&safepoint_sample_counts.gc_sample_count, samples);
 			if (atomic::load(&current_jit_count) > 0)
 				atomic::add(&safepoint_sample_counts.jit_sample_count, samples);
-			if (pc != 0 && !code->seg->in_segment_p(pc))
+			if (!code->seg->in_segment_p(pc))
 				atomic::add(&safepoint_sample_counts.foreign_sample_count, samples);
 		}
 		code->guard_safepoint();

vm/vm.cpp

@@ -3,8 +3,9 @@
 namespace factor
 {
 
-factor_vm::factor_vm() :
+factor_vm::factor_vm(THREADHANDLE thread) :
 	nursery(0,0),
+        thread(thread),
 	callback_id(0),
 	c_to_factor_func(NULL),
 	counting_profiler_p(false),

vm/vm.hpp

@@ -36,6 +36,9 @@ struct factor_vm
 	// ^^^^^^
 	//
 
+        /* Handle to the main thread we run in */
+        THREADHANDLE thread;
+
 	/* Data stack and retain stack sizes */
 	cell datastack_size, retainstack_size, callstack_size;
 
@@ -754,7 +757,7 @@ struct factor_vm
 	void call_fault_handler(exception_type_t exception, exception_data_type_t code, MACH_EXC_STATE_TYPE *exc_state, MACH_THREAD_STATE_TYPE *thread_state, MACH_FLOAT_STATE_TYPE *float_state);
   #endif
 
-	factor_vm();
+	factor_vm(THREADHANDLE thread_id);
 	~factor_vm();
 };