test(xcat-dep): a build that deadlocks under emulation hangs the pipeline

A riscv64 goconserver `go build` sat 26 minutes with zero CPU ticks across a
20-second sample, both Go pids in futex_wait and no socket open. Nothing bounds
a build step, so the cell did not fail -- it hung, and a hung run reads as
"still running" rather than as a defect.

t/build_timeout.t drives the bounded path with a command that hangs and asserts
that the call returns, reports a timeout, and prints the process tree, each
pid's wchan, the open socket count and a CPU-tick sample. A second case drives a
spinning command and asserts the report calls it slow, not deadlocked, so the
sample means something.

Each call under test runs in a forked child whose stdio is detached to a file,
and the parent bounds that child. An unbounded run must fail this test, not
block prove.

Signed-off-by: Daniel Hilst <392820+dhilst@users.noreply.github.com>

.github/workflows/genesis-openembedded.yml

@@ -55,5 +55,6 @@ jobs:
       - name: Run package tests
         run: |
           prove -v t/build_utils.t
+          prove -v t/build_timeout.t
           prove -v -It/lib t/genesis_openembedded_release.t
           sudo -E prove -v -It/lib t/genesis_openembedded_consumer.t

t/build_timeout.t

@@ -0,0 +1,131 @@
+#!/usr/bin/perl
+# Behaviour test for the wall-clock bound on emulated build steps. It DRIVES run_bounded with a
+# command that hangs and asserts that the call returns, fails, and prints the evidence -- it never
+# reads the source of the thing it tests.
+#
+# Every call under test runs in a forked child whose stdio is detached to a file, and the parent
+# bounds that child itself. Without the bound in run_bounded the child would block forever; a child
+# holding this test's stdout would block prove instead of failing it, so the failure of the code
+# under test must show up as a FAILED assertion here, never as a hung suite.
+use strict;
+use warnings;
+
+use File::Temp qw(tempdir);
+use FindBin;
+use POSIX ();
+use Test::More;
+
+use lib "$FindBin::Bin/../lib", "$FindBin::Bin/..";
+use XCAT::BuildUtils qw(run_bounded emulated_build_timeout);
+use BuildUtils qw(chroot_build_timeout);
+
+my $tmp = tempdir(CLEANUP => 1);
+my @strays;
+# waitpid on an already-gone child sets $? to -1, and Test::Builder's END reads $? as the exit
+# status. Save it, or a clean run reports "exited with -1".
+END { local $?; for my $p (@strays) { kill('KILL', $p); waitpid($p, 0); } }
+
+# drive(): run one run_bounded call in a detached child and wait at most {deadline} seconds for it.
+# Returns the child's result plus whether it finished on its own -- "did not finish" is the assertion
+# that catches an unbounded run_bounded, which would otherwise hang this test.
+sub drive {
+    my (%a) = @_;
+    my $out = "$tmp/$a{name}.out";
+    my $res = "$tmp/$a{name}.res";
+    my $t0  = time;
+
+    my $pid = fork();
+    die "fork: $!" unless defined $pid;
+    if ($pid == 0) {
+        open(STDIN,  '<',  '/dev/null');
+        open(STDOUT, '>',  $out) or POSIX::_exit(90);
+        open(STDERR, '>&', \*STDOUT);
+        POSIX::setpgid(0, 0);
+        my $r = eval {
+            run_bounded(cmd => $a{cmd}, timeout => $a{timeout},
+                        sample => $a{sample}, label => $a{name}, out => \*STDOUT);
+        } || { ec => -99, timed_out => 0, elapsed => -1 };
+        if (open(my $fh, '>', $res)) { print {$fh} "$r->{ec} $r->{timed_out} $r->{elapsed}\n"; close($fh); }
+        POSIX::_exit(0);
+    }
+    POSIX::setpgid($pid, $pid);
+
+    my $deadline = $t0 + $a{deadline};
+    my $finished = 0;
+    while (time < $deadline) {
+        if (waitpid($pid, POSIX::WNOHANG()) == $pid) { $finished = 1; last; }
+        select(undef, undef, undef, 0.2);
+    }
+    # Reap unconditionally: an unreaped child keeps its group alive and the next test inherits it.
+    unless ($finished) { kill('KILL', -$pid); waitpid($pid, 0); }
+
+    my ($ec, $timed_out, $elapsed) = (-1, 0, -1);
+    if (open(my $fh, '<', $res)) { ($ec, $timed_out, $elapsed) = split(' ', <$fh> // ''); close($fh); }
+    my $text = '';
+    if (open(my $fh, '<', $out)) { local $/; $text = <$fh> // ''; close($fh); }
+    return { finished => $finished, ec => $ec, timed_out => $timed_out,
+             elapsed => $elapsed, out => $text, wall => time - $t0 };
+}
+
+# --- the budget itself -----------------------------------------------------------------------
+is(emulated_build_timeout('amd64', 'amd64'), 900, 'a native build gets the native budget');
+is(emulated_build_timeout('riscv64', 'amd64'), 9000,
+    'an emulated build gets ten times the native budget');
+{
+    local $ENV{XCAT_DEP_BUILD_TIMEOUT} = 42;
+    is(chroot_build_timeout('noble-riscv64-sbuild'), 42, 'XCAT_DEP_BUILD_TIMEOUT overrides the budget');
+}
+{
+    local %ENV = %ENV; delete $ENV{XCAT_DEP_BUILD_TIMEOUT};
+    is(chroot_build_timeout('noble-riscv64-sbuild'), 9000,
+        'a riscv64 chroot on this host derives the emulated budget');
+}
+
+# --- a command that exits normally is not touched --------------------------------------------
+my $ok = drive(name => 'exit0', cmd => 'exit 0', timeout => 60, sample => 1, deadline => 30);
+ok($ok->{finished}, 'a fast command returns');
+is($ok->{ec}, 0, 'its exit status is 0');
+is($ok->{timed_out}, 0, 'it is not reported as timed out');
+
+my $bad = drive(name => 'exit3', cmd => 'exit 3', timeout => 60, sample => 1, deadline => 30);
+is($bad->{ec}, 3, 'a failing command keeps its exit status');
+
+# --- THE DEFECT: a build that hangs must fail, within the budget, with evidence ---------------
+my $hang = drive(name => 'hang', cmd => 'exec sleep 600 >/dev/null 2>&1',
+                 timeout => 4, sample => 2, deadline => 90);
+ok($hang->{finished}, 'a hanging command does NOT hang the caller')
+    or BAIL_OUT('run_bounded never returned: the bound is missing, so a hung build has no failure');
+is($hang->{timed_out}, 1, 'the hang is reported as a timeout');
+is($hang->{ec}, 124, 'the timeout exit status is 124, as timeout(1) uses');
+cmp_ok($hang->{wall}, '<', 60, 'it fails soon after the budget, not later');
+like($hang->{out}, qr/exceeded its 4s budget/, 'the failure names the budget it exceeded');
+like($hang->{out}, qr/stall report: process group \d+/, 'it prints the process group');
+like($hang->{out}, qr/PID\s+PPID\s+STAT\s+TICKS\s+DELTA\s+WCHAN\s+CMD/, 'it prints the process tree');
+like($hang->{out}, qr/sockets: \d+/, 'it prints the open socket count');
+like($hang->{out}, qr/CPU ticks consumed by the whole group during the sample: 0/,
+    'it samples CPU ticks and finds none');
+like($hang->{out}, qr/DEADLOCKED, not slow/, 'it says the build was deadlocked rather than slow');
+
+# --- a busy build is reported differently, so the sample means something ----------------------
+my $busy = drive(name => 'busy', cmd => 'exec bash -c "while :; do :; done" >/dev/null 2>&1',
+                 timeout => 4, sample => 2, deadline => 90);
+ok($busy->{finished}, 'a spinning command is also bounded');
+is($busy->{timed_out}, 1, 'the spin is reported as a timeout');
+like($busy->{out}, qr/still consumes CPU/, 'a spinning build is NOT called deadlocked');
+unlike($busy->{out}, qr/DEADLOCKED/, 'the CPU sample distinguishes a slow build from a deadlock');
+
+# --- the whole process group dies, not just the shell ----------------------------------------
+my $pidfile = "$tmp/grandchild.pid";
+my $tree = drive(name => 'tree',
+                 cmd => "sleep 600 >/dev/null 2>&1 & echo \$! > $pidfile; wait",
+                 timeout => 4, sample => 1, deadline => 90);
+ok($tree->{finished}, 'a command with a child of its own is bounded too');
+my $gpid = 0;
+if (open(my $fh, '<', $pidfile)) { chomp($gpid = <$fh> // 0); close($fh); }
+ok($gpid > 0, 'the grandchild recorded its pid');
+push @strays, $gpid if $gpid > 0;
+my $alive = 1;
+for (1 .. 50) { $alive = (-d "/proc/$gpid") ? 1 : 0; last unless $alive; select(undef, undef, undef, 0.2); }
+is($alive, 0, 'the grandchild is killed with the group, so nothing survives holding the pipe');
+
+done_testing();