1.0.5.49: interrupt & GC & PA handling

[sbcl.git] / src / code / sysmacs.lisp

diff --git a/src/code/sysmacs.lisp b/src/code/sysmacs.lisp
index aca1cc5..ad91f85 100644 (file)
--- a/src/code/sysmacs.lisp
+++ b/src/code/sysmacs.lisp
@@ -48,14 +48,30 @@ stopped for GC while T2 is waiting for the lock inside WITHOUT-GCING the
 system will be deadlocked. Since SBCL does not currently document its internal
 locks, application code can never be certain that this invariant is
 maintained."
 system will be deadlocked. Since SBCL does not currently document its internal
 locks, application code can never be certain that this invariant is
 maintained."

-  `(unwind-protect
-        (let* ((*interrupts-enabled* nil)
-               (*gc-inhibit* t))
-          ,@body)
-     (when (or (and *interrupts-enabled* *interrupt-pending*)
-               (and (not *gc-inhibit*)
-                    (or *gc-pending* #!+sb-thread *stop-for-gc-pending*)))
-       (sb!unix::receive-pending-interrupt))))
+  (with-unique-names (without-gcing-body)
+    `(flet ((,without-gcing-body ()
+              ,@body))
+       (if *gc-inhibit*
+           (,without-gcing-body)
+           (without-interrupts
+             ;; We need to disable interrupts before disabling GC, so that
+             ;; signal handlers using locks don't accidentally try to grab
+             ;; them with GC inhibited.
+             ;;
+             ;; It would be nice to implement this with just a single UWP, but
+             ;; unfortunately it seems that it cannot be done: the naive
+             ;; solution of binding both *INTERRUPTS-ENABLED* and
+             ;; *GC-INHIBIT*, and checking for both pending GC and interrupts
+             ;; in the cleanup breaks if we have a GC pending, but no
+             ;; interrupts, and we receive an asynch unwind while checking for
+             ;; the pending GC: we unwind before handling the pending GC, and
+             ;; will be left running with further GCs blocked due to the GC
+             ;; pending flag.
+             (unwind-protect
+                  (let ((*gc-inhibit* t))
+                    (,without-gcing-body))
+               (when (or *gc-pending* #!+sb-thread *stop-for-gc-pending*)
+                 (sb!unix::receive-pending-interrupt))))))))

 
 \f
 ;;; EOF-OR-LOSE is a useful macro that handles EOF.
 
 \f
 ;;; EOF-OR-LOSE is a useful macro that handles EOF.