Subject: [bug#41444] [PATCH] Fix guile-fibers resource leak

From: Caleb Ristvedt <[email-masked]>
Date: Thu, 21 May 2020 20:52:38 -0500

This adds a patch to guile-fibers to fix a resource leak that caused
file descriptors to be opened and never closed with each invocation of
`run-fibers'.  This is presumably what was causing the tests to fail, as
guile will abort when it gets EMFILE while attempting to create a new
thread.  I've verified that it builds on my system, but it's only a
4-core machine, and the rate at which file descriptors leak scales with
the number of cores, so it's possible it would have built successfully
here regardless.  Could someone with access to a system with more cores
verify that it now builds properly there?

Hopefully a bug fix release will show up soon enough and we can get rid
of this.

- reepca

From 659fa6b70cb8364187753e240076cdb107320070 Mon Sep 17 00:00:00 2001
From: Caleb Ristvedt <[email-masked]>
Date: Thu, 21 May 2020 20:30:58 -0500
Subject: [PATCH] gnu: guile-fibers: Add patch to fix resource leak.

[email-masked] has a resource leak where run-fibers will only destroy one
scheduler, but it creates as many as there are cpu cores by default (see
https://github.com/wingo/fibers/issues/36).  This causes the tests to fail on
systems with many cores, and can cause guile to crash under certain
circumstances.  This fixes that resource leak.  At present neither git master
nor the latest release has fixed this yet.

* gnu/packages/patches/guile-fibers-destroy-peer-schedulers.patch: new patch.
* gnu/local.mk: add it to the list of patches.
* gnu/packages/guile-xyz.scm (guile-fibers): use it.
---
 gnu/local.mk                                  |  1 +
 gnu/packages/guile-xyz.scm                    |  5 +++-
 ...guile-fibers-destroy-peer-schedulers.patch | 24 +++++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 gnu/packages/patches/guile-fibers-destroy-peer-schedulers.patch

diff --git a/gnu/local.mk b/gnu/local.mk
index 1d9de9a57e..2f24f892b1 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -1053,6 +1053,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/guile-3.0-relocatable.patch		\
   %D%/packages/patches/guile-linux-syscalls.patch		\
   %D%/packages/patches/guile-3.0-linux-syscalls.patch		\
+  %D%/packages/patches/guile-fibers-destroy-peer-schedulers.patch \
   %D%/packages/patches/guile-gdbm-ffi-support-gdbm-1.14.patch	\
   %D%/packages/patches/guile-present-coding.patch		\
   %D%/packages/patches/guile-rsvg-pkgconfig.patch		\
diff --git a/gnu/packages/guile-xyz.scm b/gnu/packages/guile-xyz.scm
index 674b1f922b..a1deee32d1 100644
--- a/gnu/packages/guile-xyz.scm
+++ b/gnu/packages/guile-xyz.scm
@@ -523,7 +523,10 @@ Unix-style DSV format and RFC 4180 format.")
                     (("#:use-module \\(fibers\\)")
                      (string-append "#:use-module (fibers)\n"
                                     "#:use-module (ice-9 threads)\n")))
-                  #t))))
+                  #t))
+              (patches
+               ;; fixes a resource leak that causes crashes in the tests
+               (search-patches "guile-fibers-destroy-peer-schedulers.patch"))))
     (build-system gnu-build-system)
     (arguments
      '(;; The code uses 'scm_t_uint64' et al., which are deprecated in 3.0.
diff --git a/gnu/packages/patches/guile-fibers-destroy-peer-schedulers.patch b/gnu/packages/patches/guile-fibers-destroy-peer-schedulers.patch
new file mode 100644
index 0000000000..8bb7153153
--- /dev/null
+++ b/gnu/packages/patches/guile-fibers-destroy-peer-schedulers.patch
@@ -0,0 +1,24 @@
+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))))))
+
-- 
2.26.2