Update sys.rst

Author: impact27

Doc/library/sys.rst

@@ -1418,6 +1418,11 @@ always available.
 
    ``'c_exception'``
       A C function has raised an exception.  *arg* is the C function object.
+   
+   .. note::
+      The same tracing mechanism is used for :func:`setprofile` than :func:`settrace`.
+      To trace calls with :func:`setprofile` inside a tracing function (e.g. in a
+      debugger breakpoint) see :func:`call_tracing`.
 
 .. function:: setrecursionlimit(limit)
 
@@ -1478,6 +1483,10 @@ always available.
 
    If there is any error occurred in the trace function, it will be unset, just
    like ``settrace(None)`` is called.
+   
+   .. note::
+      Tracing is disabled while calling the trace function (e.g. a function set by
+      :func:`settrace` or :func:`setprofile`). For recursive tracing see :func:`call_tracing`.
 
    The events have the following meaning: