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
?id=8a5924dcfecf02ae755d717cd11643b8a42bd7fc&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-09-27 19:11:27 +0200'>2019-09-27</span></td><td><a href='/guix/commit/gnu/packages/texinfo.scm?id=e7f62a41b245ca30404c54f3f77930336627c2f7'>Merge branch 'master' into core-updates</a></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-09-26 23:15:28 +0200'>2019-09-26</span></td><td><a href='/guix/commit/gnu/packages/texinfo.scm?id=99fcefb94c19c25dfa77f28fc8569da6d3aca64f'>gnu: texinfo: Add version 6.7.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/texinfo.scm (texinfo-6.7): New variable.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-09-04 19:18:10 +0200'>2019-09-04</span></td><td><a href='/guix/commit/gnu/packages/texinfo.scm?id=4ab97ef18fa9923f00865c2d3f79bead247aa5e3'>Revert "gnu: texinfo: Fix cross-compilation."</a><span class='msg-avail'>...<span class='msg-tooltip'>This causes too many rebuilds for the master branch.

This reverts commit 210b6412eeb915bba0848c1a947a24bfc51b9efc.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-09-04 18:25:17 +0200'>2019-09-04</span></td><td><a href='/guix/commit/gnu/packages/texinfo.scm?id=210b6412eeb915bba0848c1a947a24bfc51b9efc'>gnu: texinfo: Fix cross-compilation.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/texinfo.scm (texinfo)[arguments]: Do not reset environment
before running configure with the native compiler, in a cross-compilation
context,
[inputs]: move perl from here ...
[native-inputs]: ... to here. Also add ncurses that is needed in a
cross-compilation context to build texinfo native tools.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-02-20 17:25:23 +0100'>2019-02-20</span></td><td><a href='/guix/commit/gnu/packages/texinfo.scm?id=b3e508dadbeb1a08592f8691a1de63bdeb43b39a'>gnu: texinfo: Update to 6.6.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/patches/texinfo-perl-compat.patch: Delete file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/texinfo.scm (texinfo): Update to 6.6.
[source](patches): Remove.
</span></span></td><td>Marius Bakke</td></tr>