+(defmacro with-interrupt-bindings (&body body)
+ `(let*
+ ;; KLUDGE: Whatever is on the PCL stacks before the interrupt
+ ;; handler runs doesn't really matter, since we're not on the
+ ;; same call stack, really -- and if we don't bind these (esp.
+ ;; the cache one) we can get a bogus metacircle if an interrupt
+ ;; handler calls a GF that was being computed when the interrupt
+ ;; hit.
+ ((sb!pcl::*cache-miss-values-stack* nil)
+ (sb!pcl::*dfun-miss-gfs-on-stack* nil))
+ ,@body))
+
+;;; Evaluate CLEANUP-FORMS iff PROTECTED-FORM does a non-local exit.
+(defmacro nlx-protect (protected-form &rest cleanup-froms)
+ (with-unique-names (completep)
+ `(let ((,completep nil))
+ (without-interrupts
+ (unwind-protect
+ (progn
+ (allow-with-interrupts
+ ,protected-form)
+ (setq ,completep t))
+ (unless ,completep
+ ,@cleanup-froms))))))
+
+(defun invoke-interruption (function)
+ (without-interrupts
+ ;; Reset signal mask: the C-side handler has blocked all
+ ;; deferrable signals before funcalling into lisp. They are to be
+ ;; unblocked the first time interrupts are enabled. With this
+ ;; mechanism there are no extra frames on the stack from a
+ ;; previous signal handler when the next signal is delivered
+ ;; provided there is no WITH-INTERRUPTS.
+ (let ((*unblock-deferrables-on-enabling-interrupts-p* t))
+ (with-interrupt-bindings
+ (let ((sb!debug:*stack-top-hint*
+ (nth-value 1 (sb!kernel:find-interrupted-name-and-frame))))
+ (sb!thread::without-thread-waiting-for (:already-without-interrupts t)
+ (allow-with-interrupts
+ (nlx-protect (funcall function)
+ ;; We've been running with deferrables
+ ;; blocked in Lisp called by a C signal
+ ;; handler. If we return normally the sigmask
+ ;; in the interrupted context is restored.
+ ;; However, if we do an nlx the operating
+ ;; system will not restore it for us.
+ (when *unblock-deferrables-on-enabling-interrupts-p*
+ ;; This means that storms of interrupts
+ ;; doing an nlx can still run out of stack.
+ (unblock-deferrable-signals))))))))))
+
+(defmacro in-interruption ((&key) &body body)
+ #!+sb-doc
+ "Convenience macro on top of INVOKE-INTERRUPTION."
+ `(dx-flet ((interruption () ,@body))
+ (invoke-interruption #'interruption)))