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))))))

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<div class='path'>path: <a href='/guix/log/?id=258a27eea9aab4f8af995f95743ccd264b5efcb5'>root</a>/<a href='/guix/log/gnu?id=258a27eea9aab4f8af995f95743ccd264b5efcb5'>gnu</a>/<a href='/guix/log/gnu/installer?id=258a27eea9aab4f8af995f95743ccd264b5efcb5'>installer</a>/<a href='/guix/log/gnu/installer/steps.scm?id=258a27eea9aab4f8af995f95743ccd264b5efcb5'>steps.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/installer/steps.scm?id=258a27eea9aab4f8af995f95743ccd264b5efcb5&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-07-04 13:04:45 +0200'>2021-07-04</span></td><td><a href='/guix/commit/gnu/installer/steps.scm?id=8dc852b9400a8693508a6c1fab66964fb5007e38'>installer: Unconditionally import (gnu services cups) in config.scm.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/steps.scm (format-configuration): Add cups to the list
of GNU service modules.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-04-14 22:51:38 +0200'>2021-04-14</span></td><td><a href='/guix/commit/gnu/installer/steps.scm?id=70c2897ea39b8633f7b71324025954e43b4ed055'>installer: Internationalize comment of the generated config.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/steps.scm (configuration-&gt;file): Pass the comment in the
generated file through 'G_'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-11-07 13:19:25 +0100'>2020-11-07</span></td><td><a href='/guix/commit/gnu/installer/steps.scm?id=8338d414b361e4fb961221642c1064e9dc89ba65'>installer: Limit listbox height.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes: &lt;https://issues.guix.gnu.org/44428&gt;.

* gnu/installer/newt.scm (init): Print screen size.
* gnu/installer/newt/page.scm (default-listbox-height): New variable.
(run-listbox-selection-page): Use it.
* gnu/installer/newt/wifi.scm (wifi-listbox-height): Ditto.
* gnu/installer/newt/network.scm (run-technology-page): Set the maximum
listbox height to 5.
* gnu/installer/newt/ethernet.scm (run-ethernet-page): Ditto.
* gnu/installer/newt/final.scm (run-config-display-page): Change listbox
height.
* gnu/installer/newt/partition.scm (run-disk-page): Ditto.
* gnu/installer/newt/welcome.scm (display-logo?): New procedure.
(run-menu-page): Use it.
* gnu/installer/steps.scm (%configuration-file-width): Remove it.
</span></span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-09-21 00:31:15 +0200'>2020-09-21</span></td><td><a href='/guix/commit/gnu/installer/steps.scm?id=e1f3788944ee154ba9b33c891c4ccf039a1ff39a'>installer: Fix docstring typoes.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/connman.scm (connman-state, run-locale-page)
(start-swapping, stop-swapping, run-installer-steps): Fix typo in
docstring.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-03-05 23:40:22 +0100'>2020-03-05</span></td><td><a href='/guix/commit/gnu/installer/steps.scm?id=63b8c089c1596cd3e814ac13e1a8b3fa45bb2b54'>installer: Implement a dialog on /var/guix/installer-socket.</a><span class='msg-avail'>...<span class='msg-tooltip'>This will allow us to automate testing of the installer.

* gnu/installer/utils.scm (%client-socket-file)
(current-server-socket, current-clients): New variables.
(open-server-socket, call-with-server-socket): New procedure.
(with-server-socket): New macro.
(run-shell-command): Add call to 'send-to-clients'.  Select on both
current-input-port and current-clients.
* gnu/installer/steps.scm (run-installer-steps): Wrap 'call-with-prompt'
in 'with-socket-server'.  Call 'sigaction' for SIGPIPE.
* gnu/installer/newt/page.scm (watch-clients!, close-port-and-reuse-fd)
(run-form-with-clients, send-to-clients): New procedures.
(draw-info-page): Add call to 'run-form-with-clients'.
(run-input-page): Likewise.  Handle EXIT-REASON equal to 'exit-fd-ready.
(run-confirmation-page): Likewise.
(run-listbox-selection-page): Likewise.  Define 'choice-&gt;item' and use it.
(run-checkbox-tree-page): Likewise.
(run-file-textbox-page): Add call to 'run-form-with-clients'.  Handle
'exit-fd-ready'.
* gnu/installer/newt/partition.scm (run-disk-page): Pass
 #:client-callback-procedure to 'run-listbox-selection-page'.
* gnu/installer/newt/user.scm (run-user-page): Call
'run-form-with-clients'.  Handle 'exit-fd-ready'.
* gnu/installer/newt/welcome.scm (run-menu-page): Define
'choice-&gt;item' and use it.  Call 'run-form-with-clients'.
* gnu/installer/newt/final.scm (run-install-success-page)
(run-install-failed-page): When (current-clients) is non-empty, call
'send-to-clients' without displaying a choice window.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-02-22 00:45:42 +0100'>2020-02-22</span></td><td><a href='/guix/commit/gnu/installer/steps.scm?id=5c04b00cf463a543b8ffc9eb55991f6b4cc145dd'>installer: Log important bits to syslog.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer.scm (installer-program): Log crashes with 'syslog'.
* gnu/installer/parted.scm (luks-format-and-open, luks-close)
(mount-user-partitions, umount-user-partitions): Add 'syslog' calls.
* gnu/installer/steps.scm (run-installer-steps): Log the running step
with 'syslog'.
* gnu/installer/utils.scm (run-shell-command): Add calls to 'syslog'.
</span></span></td><td>Ludovic Courtès</td></tr>