tests: test for parallel sort spinlock abuse

* tests/misc/sort-spinlock-abuse: New file.
* tests/Makefile.am (TESTS): Add it.
(XFAIL_TESTS): Mark this as an expected-to-fail (for now) test.

tests/Makefile.am

@@ -237,6 +237,7 @@ TESTS =						\
   misc/sort-merge-fdlimit			\
   misc/sort-month				\
   misc/sort-rand				\
+  misc/sort-spinlock-abuse			\
   misc/sort-unique				\
   misc/sort-version				\
   misc/split-a					\
@@ -654,4 +655,7 @@ pr_data =					\
   pr/ttb3-FF					\
   pr/w72l24f-ll
 
+XFAIL_TESTS =					\
+  misc/sort-spinlock-abuse
+
 include $(srcdir)/check.mk

tests/misc/sort-spinlock-abuse

@@ -0,0 +1,37 @@
+#!/bin/sh
+# trigger a bug that would make parallel sort use 100% of one or more
+# CPU while blocked on output.
+
+# Copyright (C) 2010 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+print_ver_ sort
+
+test "$(nproc)" = 1 && skip_ "requires a multi-core system"
+
+seq 100000 > in || framework_failure_
+mkfifo fifo || framework_failure_
+
+# Arrange for sort to require 1.2+ seconds of wall-clock time,
+# while actually using far less than 1 second of CPU time.
+(for i in $(seq 12); do read line; echo $i; sleep .1; done
+  cat > /dev/null) < fifo &
+
+# Limit CPU time to 1 second
+ulimit -t 1
+sort --parallel=2 in > fifo || fail=1
+
+Exit $fail