Fibers 1.0.0 has a bug in run-fibers in which peer schedulers aren't destroyed -
so if you had 4 cores, 1 would be destroyed when run-fibers returned, but the
other 3 would stay around.  Each scheduler uses 3 file descriptors, so for
machines with many cores, this resource leak adds up quickly - quickly enough
that the test suite can even fail because of it.

See https://github.com/wingo/fibers/issues/36.

This fixes that.  It should be safe to destroy the peer schedulers at the given
point because the threads that could be running them are all either dead or the
current thread.

As of May 21, 2020, this bug still existed in the 1.0.0 (latest) release and in
git master.
--- a/fibers.scm	2020-05-21 18:38:06.890690154 -0500
+++ b/fibers.scm	2020-05-21 18:38:56.395686693 -0500
@@ -137,5 +137,6 @@
              (%run-fibers scheduler hz finished? affinity))
            (lambda ()
              (stop-auxiliary-threads scheduler)))))
+      (for-each destroy-scheduler (scheduler-remote-peers scheduler))
       (destroy-scheduler scheduler)
       (apply values (atomic-box-ref ret))))))

7f4631fdf9ef0146f462a88236885a6037d7b'>refs</a><a class='active' href='/guix/log/gnu/machine/digital-ocean.scm'>log</a><a href='/guix/tree/gnu/machine/digital-ocean.scm?id=0047f4631fdf9ef0146f462a88236885a6037d7b'>tree</a><a href='/guix/commit/gnu/machine/digital-ocean.scm?id=0047f4631fdf9ef0146f462a88236885a6037d7b'>commit</a><a href='/guix/diff/gnu/machine/digital-ocean.scm?id=0047f4631fdf9ef0146f462a88236885a6037d7b'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/machine/digital-ocean.scm'>
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<div class='path'>path: <a href='/guix/log/?id=0047f4631fdf9ef0146f462a88236885a6037d7b'>root</a>/<a href='/guix/log/gnu?id=0047f4631fdf9ef0146f462a88236885a6037d7b'>gnu</a>/<a href='/guix/log/gnu/machine?id=0047f4631fdf9ef0146f462a88236885a6037d7b'>machine</a>/<a href='/guix/log/gnu/machine/digital-ocean.scm?id=0047f4631fdf9ef0146f462a88236885a6037d7b'>digital-ocean.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/machine/digital-ocean.scm?id=0047f4631fdf9ef0146f462a88236885a6037d7b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-07-25 19:11:37 +0200'>2020-07-25</span></td><td><a href='/guix/commit/gnu/machine/digital-ocean.scm?id=d51bfe242fbe6f3f8f71d723e8fe0c7bbe711ba1'>Use 'formatted-message' instead of '&amp;message' where appropriate.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu.scm (%try-use-modules): Use 'formatted-message' instead of
'&amp;message'.
* gnu/machine/digital-ocean.scm (maybe-raise-unsupported-configuration-error):
Likewise.
* gnu/machine/ssh.scm (machine-check-file-system-availability): Likewise.
(machine-check-building-for-appropriate-system): Likewise.
(deploy-managed-host): Likewise.
(maybe-raise-unsupported-configuration-error): Likewise.
* gnu/packages.scm (search-patch): Likewise.
* gnu/services.scm (%service-with-default-value): Likewise.
(files-&gt;etc-directory): Likewise.
(fold-services): Likewise.
* gnu/system.scm (locale-name-&gt;definition*): Likewise.
* gnu/system/mapped-devices.scm (check-device-initrd-modules): Likewise.
(check-luks-device): Likewise.
* guix/channels.scm (latest-channel-instance): Likewise.
* guix/cve.scm (json-&gt;cve-items): Likewise.
* guix/git-authenticate.scm (commit-signing-key): Likewise.
(commit-authorized-keys): Likewise.
(authenticate-commit): Likewise.
(verify-introductory-commit): Likewise.
* guix/remote.scm (remote-pipe-for-gexp): Likewise.
* guix/scripts/graph.scm (assert-package): Likewise.
* guix/scripts/offload.scm (private-key-from-file*): Likewise.
* guix/ssh.scm (authenticate-server*): Likewise.
(open-ssh-session): Likewise.
(remote-inferior): Likewise.
* guix/ui.scm (matching-generations): Likewise.
* guix/upstream.scm (package-update): Likewise.
* tests/channels.scm ("latest-channel-instances, missing introduction for 'guix'"):
Catch 'formatted-message?'.
("authenticate-channel, wrong first commit signer"): Likewise.
* tests/lint.scm ("patches: not found"): Adjust message string.
* tests/packages.scm ("patch not found yields a run-time error"): Catch
'formatted-message?'.
* guix/lint.scm (check-patch-file-names): Handle 'formatted-message?'.
(check-derivation): Ditto.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-02-09 23:16:45 +0100'>2020-02-09</span></td><td><a href='/guix/commit/gnu/machine/digital-ocean.scm?id=e81344428726f3dae5d2a2e7bb296f46fcde6cc5'>Update e-mail address for Jakob L. Kreuze.</a><span class='msg-avail'>...<span class='msg-tooltip'>As requested here:
&lt;https://lists.gnu.org/archive/html/guix-devel/2020-02/msg00128.html&gt;.

* .mailmap: Add an entry for Jakob.
* gnu/machine.scm, gnu/machine/digital-ocean.scm, gnu/machine/ssh.scm,
gnu/packages/admin.scm, gnu/packages/i2p.scm, gnu/packages/music.scm,
gnu/packages/web.scm, gnu/tests/reconfigure.scm, guix/scripts/deploy.scm,
guix/scripts/system/reconfigure.scm: Update their e-mail address.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-10-22 18:32:52 +0200'>2019-10-22</span></td><td><a href='/guix/commit/gnu/machine/digital-ocean.scm?id=c93994b5e43acc6048b81836d30632e015306c92'>machine: digital-ocean: Rename 'enable-ipv6' to 'enable-ipv6?'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine/digital-ocean.scm (&lt;digital-ocean-configuration&gt;)[enable-ipv6]:
Rename to...
[enable-ipv6?]: ... this.
(deploy-digital-ocean): Adjust accordingly.
* doc/guix.texi (Invoking guix deploy): Adjust accordingly.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-22 18:32:52 +0200'>2019-10-22</span></td><td><a href='/guix/commit/gnu/machine/digital-ocean.scm?id=12712817ae97eb6305deeaad68ce17c9fa212917'>machine: Implement 'digital-ocean-environment-type'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine/digital-ocean.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Invoking guix deploy): Add documentation for
'digital-ocean-configuration'.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Jakob L. Kreuze</td></tr>