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

diff --git a/NEWS b/NEWS
index 22d90d5..152a51a 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -60,6 +60,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   Also seq no longer ignores a specified step value when the end value is 1.
   [bugs introduced in coreutils-8.20]
 
+  timeout now ensures that blocking of ALRM signals is not inherited from
+  its parent, which would cause timeouts to be ignored.
+  [the bug dates back to the initial implementation]
+
 ** Changes in behavior
 
   df --total now prints '-' into the target column (mount point) of the

diff --git a/src/timeout.c b/src/timeout.c
index b163a0e..2ffd2b1 100644 (file)
--- a/src/timeout.c
+++ b/src/timeout.c
@@ -102,6 +102,16 @@ static struct option const long_options[] =
   {NULL, 0, NULL, 0}
 };
 
+static void
+unblock_signal (int sig)
+{
+  sigset_t unblock_set;
+  sigemptyset (&unblock_set);
+  sigaddset (&unblock_set, sig);
+  if (sigprocmask (SIG_UNBLOCK, &unblock_set, NULL) != 0)
+    error (0, errno, _("warning: sigprocmask"));
+}
+
 /* Start the timeout after which we'll receive a SIGALRM.
    Round DURATION up to the next representable value.
    Treat out-of-range values as if they were maximal,
@@ -110,6 +120,11 @@ static struct option const long_options[] =
 static void
 settimeout (double duration)
 {
+
+  /* We configure timers below so that SIGALRM is sent on expiry.
+     Therefore ensure we don't inherit a mask blocking SIGALRM.  */
+  unblock_signal (SIGALRM);
+
 /* timer_settime() provides potentially nanosecond resolution.
    setitimer() is more portable (to Darwin for example),
    but only provides microsecond resolution and thus is

diff --git a/tests/local.mk b/tests/local.mk
index 82daee5..6043bb6 100644 (file)
--- 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 (executable)
index 0000000..6f16ba4
--- /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;