test failures for pid_ns_kill_child tests: [FATAL src/PerfCounters.cc:319:start_counter() errno: ESRCH] Failed to initialize counter

Ran tests with current master.

Kernel: Linux 4.18.0-80.el8.x86_64
gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5)
GNU assembler version 2.30-79.el8

$> ctest -R pid_ns_kill_child
Test project /home/install/rr/build
    Start 452: pid_ns_kill_child
1/6 Test #452: pid_ns_kill_child .........................***Failed  Error regular expression found in output. Regex=[FAILED]  1.45 sec
    Start 453: pid_ns_kill_child-no-syscallbuf
2/6 Test #453: pid_ns_kill_child-no-syscallbuf ...........***Failed  Error regular expression found in output. Regex=[FAILED]  2.75 sec
    Start 454: pid_ns_kill_child_threads
3/6 Test #454: pid_ns_kill_child_threads .................   Passed    0.20 sec
    Start 455: pid_ns_kill_child_threads-no-syscallbuf
4/6 Test #455: pid_ns_kill_child_threads-no-syscallbuf ...   Passed    0.18 sec
    Start 456: pid_ns_kill_child_zombie
5/6 Test #456: pid_ns_kill_child_zombie ..................***Failed  Error regular expression found in output. Regex=[FAILED]  1.43 sec
    Start 457: pid_ns_kill_child_zombie-no-syscallbuf
6/6 Test #457: pid_ns_kill_child_zombie-no-syscallbuf ....***Failed  Error regular expression found in output. Regex=[FAILED]  1.43 sec

33% tests passed, 4 tests failed out of 6

Total Test time (real) =   7.46 sec

The following tests FAILED:
        452 - pid_ns_kill_child (Failed)
        453 - pid_ns_kill_child-no-syscallbuf (Failed)
        456 - pid_ns_kill_child_zombie (Failed)
        457 - pid_ns_kill_child_zombie-no-syscallbuf (Failed)
Errors while running CTest

$> bin/pid_ns_kill_child
EXIT-SUCCESS
$> bin/pid_ns_kill_child_zombie
EXIT-SUCCESS

As this is reproducible and does not only apply to the syscallbuf version I think that's unrelated to #3504.

Reproduce the issue with ctest -R pid_ns_kill_child and inspect src/PerfCounters.cc:319:start_counter() alongside the pid_ns_kill_child and pid_ns_kill_child_zombie tests. Compare the syscallbuf and no-syscallbuf variants and determine why ESRCH is reported despite the standalone binaries showing EXIT-SUCCESS. Done means the affected CTest cases complete without FAILED output.