- (loop
- (sb!thread:with-mutex (*already-in-gc*)
- (unless *need-to-collect-garbage* (return-from sub-gc nil))
- (without-interrupts
- (gc-stop-the-world)
- (collect-garbage gen)
- (incf *n-bytes-freed-or-purified*
- (max 0 (- pre-gc-dynamic-usage (dynamic-usage))))
- (scrub-control-stack)
- (setf *need-to-collect-garbage* nil)
- (dolist (h *after-gc-hooks*) (carefully-funcall h))
- (gc-start-the-world))
- (sb!thread::reap-dead-threads))))))
+ (sb!thread:with-mutex (*already-in-gc*)
+ (let ((old-usage (dynamic-usage))
+ (new-usage 0))
+ (unsafe-clear-roots)
+ ;; We need to disable interrupts for GC, but we also want
+ ;; to run as little as possible without them.
+ (without-interrupts
+ (gc-stop-the-world)
+ (collect-garbage gen)
+ (setf *need-to-collect-garbage* nil
+ new-usage (dynamic-usage))
+ (gc-start-the-world))
+ ;; Interrupts re-enabled, but still inside the mutex.
+ ;; In a multithreaded environment the other threads will
+ ;; see *n-b-f-o-p* change a little late, but that's OK.
+ (let ((freed (- old-usage new-usage)))
+ ;; GENCGC occasionally reports negative here, but the
+ ;; current belief is that it is part of the normal order
+ ;; of things and not a bug.
+ (when (plusp freed)
+ (incf *n-bytes-freed-or-purified* freed)))
+ (sb!thread::reap-dead-threads)))
+ ;; Outside the mutex, these may cause another GC.
+ (run-pending-finalizers)
+ (dolist (hook *after-gc-hooks*)
+ (handler-case
+ (funcall hook)
+ (error (c)
+ (warn "Error calling after GC hook ~S:~% ~S" hook c)))))))