Upstream fix for a memory leak introduced in Fibers 1.1.0 that would manifest
in shepherd:

  https://github.com/wingo/fibers/issues/65
  https://issues.guix.gnu.org/58631

diff --git a/fibers/scheduler.scm b/fibers/scheduler.scm
index 2b03941..760b037 100644
--- a/fibers/scheduler.scm
+++ b/fibers/scheduler.scm
@@ -182,8 +182,10 @@ remote kernel thread."
     (#f (warn "scheduler for unknown fd" fd))
     ((and events+waiters (active-events . waiters))
      ;; First, clear the active status, as the EPOLLONESHOT has
-     ;; deactivated our entry in the epoll set.
-     (set-car! events+waiters #f)
+     ;; deactivated our entry in the epoll set.  Set the car to 0, not #f, so
+     ;; that 'schedule-tasks-for-active-fd' doesn't end up re-adding a
+     ;; finalizer on FD.
+     (set-car! events+waiters 0)
      (set-cdr! events+waiters '())
      (unless (zero? (logand revents (logior EPOLLHUP EPOLLERR)))
        (hashv-remove! (scheduler-fd-waiters sched) fd))
@@ -336,21 +338,19 @@ expressed as an epoll bitfield."
 
   (let ((fd-waiters (hashv-ref (scheduler-fd-waiters sched) fd)))
     (match fd-waiters
-      ((active-events . waiters)
-       (set-cdr! fd-waiters (acons events task waiters))
-       (unless (and active-events
-                    (= (logand events active-events) events))
-         (let ((active-events (logior events (or active-events 0))))
-           (set-car! fd-waiters active-events)
-           (add-fdes-finalizer! fd (fd-finalizer fd-waiters))
-           (epoll-add*! (scheduler-epfd sched) fd
-                        (logior active-events EPOLLONESHOT)))))
-      (#f
+      ((or #f (#f))                               ;FD is new or was finalized
        (let ((fd-waiters (list events (cons events task))))
          (hashv-set! (scheduler-fd-waiters sched) fd fd-waiters)
          (add-fdes-finalizer! fd (fd-finalizer fd-waiters))
          (epoll-add*! (scheduler-epfd sched) fd
-                      (logior events EPOLLONESHOT)))))))
+                      (logior events EPOLLONESHOT))))
+      ((active-events . waiters)
+       (set-cdr! fd-waiters (acons events task waiters))
+       (unless (= (logand events active-events) events)
+         (let ((active-events (logior events active-events)))
+           (set-car! fd-waiters active-events)
+           (epoll-add*! (scheduler-epfd sched) fd
+                        (logior active-events EPOLLONESHOT))))))))
 
 (define (schedule-task-when-fd-readable sched fd task)
   "Arrange to schedule @var{task} on @var{sched} when the file
11b96eb5493231a5a35045505ff8ae8aa746b8e'>etc: Add explicit ‘--substitute-urls’ in guix-daemon service files.</a><span class='msg-avail'>...<span class='msg-tooltip'>Having substitute URLs explicitly listed in the service startup file
makes it clearer what should be modified to permanently change the list
of substitute URLs.

* config-daemon.ac: Rename ‘guix_substitute_urls’ to
‘GUIX_SUBSTITUTE_URLS’ and substitute it.
* nix/local.mk (etc/guix-%.service, etc/init.d/guix-daemon)
(etc/guix-%.conf): Substitute it.
* etc/guix-daemon.conf.in, etc/guix-daemon.service.in,
etc/init.d/guix-daemon.in: Add an explicit ‘--substitute-urls’ option.

Change-Id: Ie491b7fab5c42e54dca582801c03805a85de2bf9
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-07-07 23:54:20 -0400'>2021-07-07</span></td><td><a href='/guix/commit/etc/init.d?id=4cbe0127a668cbcc64087c5d311308b59d39b104'>guix-install.sh: Prompt for configuring substitutes discovery.</a><span class='msg-avail'>...<span class='msg-tooltip'>Also ensure prompt_yes_no always print the message with a trailing space,
which is more pleasing to the eye.

* etc/guix-daemon.conf.in &lt;--discover=no&gt;: New guix-daemon option.
* etc/guix-daemon.service.in: Likewise.
* etc/init.d/guix-daemon.in: Likewise.
* etc/openrc/guix-daemon.in: Likewise.
* etc/guix-install.sh (configure_substitute_discovery): New procedure.
(sys_enable_guix_daemon): Ask the user whether automatic substitute discovery
should be enabled.  Set the '--discover' argument accordingly.
(prompt_yes_no): Add a trailing space to the message.
(sys_authorize_build_farms): Remove trailing space from the message argument.
* NEWS (Distribution): Add news.
</span></span></td><td>Maxim Cournoyer</td></tr>