From 127b1171132062664c9b1ec6641d4fa48f1f27b2 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Fri, 15 Jan 2016 16:35:12 +0000
Subject: [PATCH] Add @host_only function decorator (#172).

---
 artiq/compiler/embedding.py |  6 ++++++
 artiq/frontend/artiq_run.py |  1 +
 artiq/language/core.py      | 22 +++++++++++++++++-----
 artiq/master/worker_impl.py |  1 +
 4 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/artiq/compiler/embedding.py b/artiq/compiler/embedding.py
index 4adb38814..fb185a39b 100644
--- a/artiq/compiler/embedding.py
+++ b/artiq/compiler/embedding.py
@@ -739,6 +739,12 @@ class Stitcher:
                     # to perform a system call instead of a regular call.
                     result = self._quote_foreign_function(function, loc,
                                                           syscall=function.artiq_embedded.syscall)
+                elif function.artiq_embedded.forbidden is not None:
+                    diag = diagnostic.Diagnostic("fatal",
+                        "this function cannot be called as an RPC", {},
+                        self._function_loc(function),
+                        notes=self._call_site_note(loc, is_syscall=True))
+                    self.engine.process(diag)
                 else:
                     assert False
             else:
diff --git a/artiq/frontend/artiq_run.py b/artiq/frontend/artiq_run.py
index 4bb33c606..a51b8083e 100755
--- a/artiq/frontend/artiq_run.py
+++ b/artiq/frontend/artiq_run.py
@@ -60,6 +60,7 @@ class DummyScheduler:
     def get_status(self):
         return dict()
 
+    @host_only
     def pause(self):
         pass
 
diff --git a/artiq/language/core.py b/artiq/language/core.py
index f32b598ee..a374562a9 100644
--- a/artiq/language/core.py
+++ b/artiq/language/core.py
@@ -11,7 +11,7 @@ from artiq.coredevice.runtime import source_loader
 
 
 __all__ = ["host_int", "int", "host_round", "round",
-           "kernel", "portable", "syscall",
+           "kernel", "portable", "syscall", "host_only",
            "set_time_manager", "set_watchdog_factory",
            "ARTIQException",
            "TerminationRequested"]
@@ -168,7 +168,7 @@ def round(value, width=32):
 
 
 _ARTIQEmbeddedInfo = namedtuple("_ARTIQEmbeddedInfo",
-                                "core_name function syscall")
+                                "core_name function syscall forbidden")
 
 def kernel(arg):
     """
@@ -196,7 +196,8 @@ def kernel(arg):
             def run_on_core(self, *k_args, **k_kwargs):
                 return getattr(self, arg).run(run_on_core, ((self,) + k_args), k_kwargs)
             run_on_core.artiq_embedded = _ARTIQEmbeddedInfo(
-                core_name=arg, function=function, syscall=None)
+                core_name=arg, function=function, syscall=None,
+                forbidden=False)
             return run_on_core
         return inner_decorator
     else:
@@ -213,7 +214,8 @@ def portable(function):
     on the core device (no RPC).
     """
     function.artiq_embedded = \
-        _ARTIQEmbeddedInfo(core_name=None, function=function, syscall=None)
+        _ARTIQEmbeddedInfo(core_name=None, function=function, syscall=None,
+                           forbidden=False)
     return function
 
 def syscall(arg):
@@ -231,12 +233,22 @@ def syscall(arg):
         def inner_decorator(function):
             function.artiq_embedded = \
                 _ARTIQEmbeddedInfo(core_name=None, function=None,
-                                   syscall=function.__name__)
+                                   syscall=function.__name__, forbidden=False)
             return function
         return inner_decorator
     else:
         return syscall(arg.__name__)(arg)
 
+def host_only(function):
+    """
+    This decorator marks a function so that it can only be executed
+    in the host Python interpreter.
+    """
+    function.artiq_embedded = \
+        _ARTIQEmbeddedInfo(core_name=None, function=None, syscall=None,
+                           forbidden=True)
+    return function
+
 
 class _DummyTimeManager:
     def _not_implemented(self, *args, **kwargs):
diff --git a/artiq/master/worker_impl.py b/artiq/master/worker_impl.py
index db3f33c20..13ecf9b61 100644
--- a/artiq/master/worker_impl.py
+++ b/artiq/master/worker_impl.py
@@ -93,6 +93,7 @@ set_watchdog_factory(Watchdog)
 class Scheduler:
     pause_noexc = staticmethod(make_parent_action("pause"))
 
+    @host_only
     def pause(self):
         if self.pause_noexc():
             raise TerminationRequested