sort: fix hang with sort --compress

* NEWS: Document this.
* src/sort.c (UNCOMPRESSED, UNREAPED, REAPED): New constants.
(struct tempnode): New member 'state', to hold these constants.
The pid member is now undefined if state == UNCOMPRESSED.
(struct sortfile): Replace member 'pid' with member 'temp'.
(uintptr): Remove.
(proctab_hasher, proctab_comparator, register_proc, delete_proc):
Proctab entries are now struct tempnode *, not pid_t, to handle
the case where multiple tempnode objects correspond to the same
pid.  This avoids a race condition that can cause a hang.
(register_proc): Arg is now struct tempnode *, not pid_t.  All
callers changed.
(delete_proc): Set tempnode state to REAPED.
(create_temp_file): No need to set pid member here; it's now
done when the pid is known.
(maybe_create_temp, create_temp): Remove PPID arg.  Return struct
tempnode *, not char *.  All callers changed.
(maybe_create_temp): Set node state to UNCOMPRESSED or UNREAPED.
No need to set node->pid to 0.
(open_temp): Replace NAME and PID args with a single TEMP arg.
All callers changed.  Wait only for unreaped children.
(zaptemp): Wait for decompressor to finish before removing its
temporary-file input.  This avoids .nfsXXXX hassles with NFS
and fixes a race (leading to a hang) regardless of NFS.
(open_input_files): Adjust to new way of dealing with temp files
and their subprocesses.
* tests/Makefile.am (TESTS): Add misc/sort-compress-hang.
* tests/misc/sort-compress-hang: New file.

2 files changed, 54 insertions, 0 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index de0670485..06d81f06f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -228,6 +228,7 @@ TESTS =						\
   misc/sort					\
   misc/sort-benchmark-random			\
   misc/sort-compress				\
+  misc/sort-compress-hang			\
   misc/sort-compress-proc			\
   misc/sort-continue				\
   misc/sort-debug-keys				\
diff --git a/tests/misc/sort-compress-hang b/tests/misc/sort-compress-hang
new file mode 100755
index 000000000..a536b1f6b
--- /dev/null
+++ b/tests/misc/sort-compress-hang
@@ -0,0 +1,53 @@
+#!/bin/sh
+# Test for sort --compress hang
+
+# 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
+very_expensive_
+
+cat <<\EOF >compress || framework_failure
+#!/bin/sh
+tr 41 14 || exit
+touch ok
+EOF
+
+chmod +x compress
+
+seq -w 200000 > exp || fail=1
+tac exp > in || fail=1
+
+# When the bug occurs, 'sort' hangs forever.  When it doesn't occur,
+# 'sort' could be running slowly on an overburdened machine.
+# On a circa-2010 Linux server using NFS, a successful test completes
+# in about 170 seconds, so specify 1700 seconds as a safety margin.
+timeout 1700 sort --compress-program=./compress -S 1k in > out || fail=1
+
+compare exp out || fail=1
+test -f ok || fail=1
+rm -f compress ok
+
+# If $TMPDIR is relative, give subprocesses time to react when 'sort' exits.
+# Otherwise, under NFS, when 'sort' unlinks the temp files and they
+# are renamed to .nfsXXXX instead of being removed, the parent cleanup
+# of this directory will fail because the files are still open.
+case $TMPDIR in
+/*) ;;
+*) sleep 1;;
+esac
+
+Exit $fail