timeout: ensure a blocked SIGALRM from the parent is unblocked

* src/timeout.c (unblock_signal): A new function to unblock a
specified signal, or warn if not possible.
(set_timeout): Ensure SIGALRM is unblocked before we setup the timer.
* tests/misc/timeout-blocked.pl: A new test for the issue.
* tests/local.mk: Reference the new test.
* NEWS: Mention the fix.
Fixes: http://bugs.gnu.org/13535

2 files changed, 49 insertions, 0 deletions

diff --git a/tests/local.mk b/tests/local.mk
index 82daee5cd..6043bb6bd 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -369,6 +369,7 @@ all_tests =					\
   tests/misc/tee-dash.sh			\
   tests/misc/test-diag.pl			\
   tests/misc/timeout.sh				\
+  tests/misc/timeout-blocked.pl			\
   tests/misc/timeout-group.sh			\
   tests/misc/timeout-parameters.sh		\
   tests/misc/tr.pl				\
diff --git a/tests/misc/timeout-blocked.pl b/tests/misc/timeout-blocked.pl
new file mode 100755
index 000000000..6f16ba4c8
--- /dev/null
+++ b/tests/misc/timeout-blocked.pl
@@ -0,0 +1,48 @@
+#!/usr/bin/perl
+# Test that timeout handles blocked SIGALRM from its parent.
+
+# Copyright (C) 2013 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/>.
+
+use strict;
+
+(my $ME = $0) =~ s|.*/||;
+
+eval { require POSIX; };
+$@
+  and CuSkip::skip "$ME: this script requires Perl's POSIX module\n";
+
+use POSIX qw(:signal_h);
+my $sigset = POSIX::SigSet->new(SIGALRM); # define the signals to block
+my $old_sigset = POSIX::SigSet->new;      # where the old sigmask will be kept
+unless (defined sigprocmask(SIG_BLOCK, $sigset, $old_sigset)) {
+  CuSkip::skip "$ME: sigprocmask failed; skipped";
+}
+
+my @Tests =
+    (
+     # test-name, [option, option, ...] {OUT=>"expected-output"}
+     #
+
+     ['block-alrm',  ".1 sleep 10", {EXIT => 124}],
+    );
+
+my $save_temps = $ENV{DEBUG};
+my $verbose = $ENV{VERBOSE};
+
+my $prog = 'timeout';
+my $fail = run_tests ($ME, $prog, \@Tests, $save_temps, $verbose);
+
+exit $fail;