1.0.17.21: LIST-FILL* return value (regression 1.0.12.16)

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

diff --git a/src/code/timer.lisp b/src/code/timer.lisp
index 3280bd2..36235ac 100644 (file)
--- a/src/code/timer.lisp
+++ b/src/code/timer.lisp
@@ -65,7 +65,7 @@
     (aref heap 0)))
 
 (defun heap-extract (heap i &key (key #'identity) (test #'>=))
-  (when (< (length heap) i)
+  (unless (> (length heap) i)
     (error "Heap underflow"))
   (prog1
       (aref heap i)
@@ -135,8 +135,6 @@
   ;; FUNCTION until the other is called, from when it does nothing.
   (let ((mutex (sb!thread:make-mutex))
         (cancelled-p nil))
-    #!-sb-thread
-    (declare (ignore mutex))
     (list
      #'(lambda ()
          (sb!thread:with-recursive-lock (mutex)
@@ -202,10 +200,9 @@ from now. For timers with a repeat interval it returns true."
 (defvar *scheduler-lock* (sb!thread:make-mutex :name "Scheduler lock"))
 
 (defmacro with-scheduler-lock ((&optional) &body body)
-  ;; don't let the SIGALRM handler mess things up
-  `(sb!sys:without-interrupts
-    (sb!thread:with-mutex (*scheduler-lock*)
-      ,@body)))
+  ;; Don't let the SIGALRM handler mess things up.
+  `(sb!thread::with-system-mutex (*scheduler-lock*)
+     ,@body))
 
 (defun under-scheduler-lock-p ()
   #!-sb-thread
@@ -296,10 +293,13 @@ triggers."
 ;;; Not public, but related
 
 (defun reschedule-timer (timer)
-  (with-scheduler-lock ()
-    (setf (%timer-expire-time timer) (+ (get-internal-real-time)
-                                        (%timer-repeat-interval timer)))
-    (%schedule-timer timer)))
+  (let ((thread (%timer-thread timer)))
+    (if (and (sb!thread::thread-p thread) (not (sb!thread:thread-alive-p thread)))
+        (unschedule-timer timer)
+        (with-scheduler-lock ()
+          (setf (%timer-expire-time timer) (+ (get-internal-real-time)
+                                              (%timer-repeat-interval timer)))
+          (%schedule-timer timer)))))
 
 ;;; Expiring timers
 
@@ -337,7 +337,9 @@ triggers."
            (handler-case
                (sb!thread:interrupt-thread thread function)
              (sb!thread:interrupt-thread-error (c)
-               (warn c)))))))
+               (declare (ignore c))
+               (warn "Timer ~S failed to interrupt thread ~S."
+                     timer thread)))))))
 
 ;; Called from the signal handler.
 (defun run-expired-timers ()
@@ -359,8 +361,26 @@ triggers."
 
 (defmacro sb!ext:with-timeout (expires &body body)
   #!+sb-doc
-  "Execute the body, asynchronously interrupting it and signalling a
-TIMEOUT condition after at least EXPIRES seconds have passed."
+  "Execute the body, asynchronously interrupting it and signalling a TIMEOUT
+condition after at least EXPIRES seconds have passed.
+
+Note that it is never safe to unwind from an asynchronous condition. Consider:
+
+  (defun call-with-foo (function)
+    (let (foo)
+      (unwind-protect
+         (progn
+           (setf foo (get-foo))
+           (funcall function foo))
+       (when foo
+         (release-foo foo)))))
+
+If TIMEOUT occurs after GET-FOO has executed, but before the assignment, then
+RELEASE-FOO will be missed. While individual sites like this can be made proof
+against asynchronous unwinds, this doesn't solve the fundamental issue, as all
+the frames potentially unwound through need to be proofed, which includes both
+system and application code -- and in essence proofing everything will make
+the system uninterruptible."
   (with-unique-names (timer)
     ;; FIXME: a temporary compatibility workaround for CLX, if unsafe
     ;; unwinds are handled revisit it.