RE: [PATCH v2 1/6] selftests/resctrl: Extend signal handler coverage to unmount on receiving signal

[Shaopeng Tan (Fujitsu)]

Hello


> On 9/15/2023 8:44 AM, Ilpo Järvinen wrote:
> > Unmounting resctrl FS has been moved into the per test functions in
> > resctrl_tests.c by commit caddc0fbe495 ("selftests/resctrl: Move
> > resctrl FS mount/umount to higher level"). In case a signal (SIGINT,
> > SIGTERM, or SIGHUP) is received, the running selftest is aborted by
> > ctrlc_handler() which then unmounts resctrl fs before exiting. The
> > current section between signal_handler_register() and
> > signal_handler_unregister(), however, does not cover the entire
> > duration when resctrl FS is mounted.
> >
> > Move signal_handler_register() and signal_handler_unregister() calls
> > from per test files into resctrl_tests.c to properly unmount resctrl
> > fs. In order to not add signal_handler_register()/unregister() n
> > times, create helpers test_prepare() and test_cleanup().
> >
> > Adjust child process kill() call in ctrlc_handler() to only be invoked
> > if the child was already forked.
> >
> > Fixes: caddc0fbe495 ("selftests/resctrl: Move resctrl FS mount/umount
> > to higher level")
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > ---
> >  tools/testing/selftests/resctrl/cat_test.c    |  8 ---
> >  .../testing/selftests/resctrl/resctrl_tests.c | 65
> > +++++++++++--------  tools/testing/selftests/resctrl/resctrl_val.c |
> > 22 +++----
> >  3 files changed, 48 insertions(+), 47 deletions(-)
> >
> > diff --git a/tools/testing/selftests/resctrl/cat_test.c
> > b/tools/testing/selftests/resctrl/cat_test.c
> > index 97b87285ab2a..224ba8544d8a 100644
> > --- a/tools/testing/selftests/resctrl/cat_test.c
> > +++ b/tools/testing/selftests/resctrl/cat_test.c
> > @@ -167,12 +167,6 @@ int cat_perf_miss_val(int cpu_no, int n, char
> *cache_type)
> >  		strcpy(param.filename, RESULT_FILE_NAME1);
> >  		param.num_of_runs = 0;
> >  		param.cpu_no = sibling_cpu_no;
> > -	} else {
> > -		ret = signal_handler_register();
> > -		if (ret) {
> > -			kill(bm_pid, SIGKILL);
> > -			goto out;
> > -		}
> >  	}
> >
> >  	remove(param.filename);
> > @@ -209,10 +203,8 @@ int cat_perf_miss_val(int cpu_no, int n, char
> *cache_type)
> >  		}
> >  		close(pipefd[0]);
> >  		kill(bm_pid, SIGKILL);
> > -		signal_handler_unregister();
> >  	}
> >
> > -out:
> >  	cat_test_cleanup();
> >
> >  	return ret;
> > diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c
> > b/tools/testing/selftests/resctrl/resctrl_tests.c
> > index 823672a20a43..524ba83d7568 100644
> > --- a/tools/testing/selftests/resctrl/resctrl_tests.c
> > +++ b/tools/testing/selftests/resctrl/resctrl_tests.c
> > @@ -67,21 +67,41 @@ void tests_cleanup(void)
> >  	cat_test_cleanup();
> >  }
> >
> > -static void run_mbm_test(const char * const *benchmark_cmd, int
> > cpu_no)
> > +static int test_prepare()
> >  {
> >  	int res;
> >
> > -	ksft_print_msg("Starting MBM BW change ...\n");
> > +	res = signal_handler_register();
> > +	if (res)
> > +		return res;
> >
> >  	res = mount_resctrlfs();
> >  	if (res) {
> > +		signal_handler_unregister();
> >  		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
> > -		return;
> > +		return res;
> >  	}
> > +	return 0;
> > +}
> > +
> > +static void test_cleanup()
> > +{
> > +	umount_resctrlfs();
> > +	signal_handler_unregister();
> > +}
> 
> Thank you for adding these.
> 
> > +
> > +static void run_mbm_test(const char * const *benchmark_cmd, int
> > +cpu_no) {
> > +	int res;
> > +
> > +	ksft_print_msg("Starting MBM BW change ...\n");
> > +
> > +	if (test_prepare())
> > +		return;
> >
> 
> I am not sure about this. With this exit the kselftest machinery is not aware of
> the test passing or failing. I wonder if there should not rather be a "goto" here
> that triggers ksft_test_result()? This needs some more thought though. First,
> with this change test_prepare() officially gains responsibility to determine if a
> failure is transient (just a single test
> fails) or permanent (no use trying any other tests if this fails). For the former it
> would then be up to the caller to call ksft_test_result() and for the latter
> test_prepare() will call ksft_exit_fail_msg().
> Second, that SNC warning may be an inconvenience with a new goto. Here it
> may be ok to print that message before the test failure?

If a failure may be permanent, it may be best to detect it before running all tests, rather than in test_prepare().
Now some detections are completed before running all tests. For example:
273         if (geteuid() != 0)
274                 return ksft_exit_skip("Not running as root. Skipping...\n");
275
276         if (!check_resctrlfs_support())
277                 return ksft_exit_skip("resctrl FS does not exist. Enable X86_CPU_RESCTRL config option.\n");
278
279         if (umount_resctrlfs())
280                 return ksft_exit_skip("resctrl FS unmount failed.\n");

Best regards,
Shaopeng TAN

> >  	if (!validate_resctrl_feature_request(MBM_STR) || (get_vendor() !=
> ARCH_INTEL)) {
> >  		ksft_test_result_skip("Hardware does not support MBM or
> MBM is disabled\n");
> > -		goto umount;
> > +		goto cleanup;
> >  	}
> >
> >  	res = mbm_bw_change(cpu_no, benchmark_cmd); @@ -89,8 +109,8
> @@
> > static void run_mbm_test(const char * const *benchmark_cmd, int cpu_no)
> >  	if ((get_vendor() == ARCH_INTEL) && res)
> >  		ksft_print_msg("Intel MBM may be inaccurate when
> Sub-NUMA
> > Clustering is enabled. Check BIOS configuration.\n");
> >
> > -umount:
> > -	umount_resctrlfs();
> > +cleanup:
> > +	test_cleanup();
> >  }
> >
> >  static void run_mba_test(const char * const *benchmark_cmd, int
> > cpu_no) @@ -99,22 +119,19 @@ static void run_mba_test(const char *
> > const *benchmark_cmd, int cpu_no)
> >
> >  	ksft_print_msg("Starting MBA Schemata change ...\n");
> >
> > -	res = mount_resctrlfs();
> > -	if (res) {
> > -		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
> > +	if (test_prepare())
> >  		return;
> > -	}
> >
> >  	if (!validate_resctrl_feature_request(MBA_STR) || (get_vendor() !=
> ARCH_INTEL)) {
> >  		ksft_test_result_skip("Hardware does not support MBA or
> MBA is disabled\n");
> > -		goto umount;
> > +		goto cleanup;
> >  	}
> >
> >  	res = mba_schemata_change(cpu_no, benchmark_cmd);
> >  	ksft_test_result(!res, "MBA: schemata change\n");
> >
> > -umount:
> > -	umount_resctrlfs();
> > +cleanup:
> > +	test_cleanup();
> >  }
> >
> >  static void run_cmt_test(const char * const *benchmark_cmd, int
> > cpu_no) @@ -123,15 +140,12 @@ static void run_cmt_test(const char *
> > const *benchmark_cmd, int cpu_no)
> >
> >  	ksft_print_msg("Starting CMT test ...\n");
> >
> > -	res = mount_resctrlfs();
> > -	if (res) {
> > -		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
> > +	if (test_prepare())
> >  		return;
> > -	}
> >
> >  	if (!validate_resctrl_feature_request(CMT_STR)) {
> >  		ksft_test_result_skip("Hardware does not support CMT or
> CMT is disabled\n");
> > -		goto umount;
> > +		goto cleanup;
> >  	}
> >
> >  	res = cmt_resctrl_val(cpu_no, 5, benchmark_cmd); @@ -139,8 +153,8
> @@
> > static void run_cmt_test(const char * const *benchmark_cmd, int cpu_no)
> >  	if ((get_vendor() == ARCH_INTEL) && res)
> >  		ksft_print_msg("Intel CMT may be inaccurate when
> Sub-NUMA
> > Clustering is enabled. Check BIOS configuration.\n");
> >
> > -umount:
> > -	umount_resctrlfs();
> > +cleanup:
> > +	test_cleanup();
> >  }
> >
> >  static void run_cat_test(int cpu_no, int no_of_bits) @@ -149,22
> > +163,19 @@ static void run_cat_test(int cpu_no, int no_of_bits)
> >
> >  	ksft_print_msg("Starting CAT test ...\n");
> >
> > -	res = mount_resctrlfs();
> > -	if (res) {
> > -		ksft_exit_fail_msg("Failed to mount resctrl FS\n");
> > +	if (test_prepare())
> >  		return;
> > -	}
> >
> >  	if (!validate_resctrl_feature_request(CAT_STR)) {
> >  		ksft_test_result_skip("Hardware does not support CAT or CAT
> is disabled\n");
> > -		goto umount;
> > +		goto cleanup;
> >  	}
> >
> >  	res = cat_perf_miss_val(cpu_no, no_of_bits, "L3");
> >  	ksft_test_result(!res, "CAT: test\n");
> >
> > -umount:
> > -	umount_resctrlfs();
> > +cleanup:
> > +	test_cleanup();
> >  }
> >
> >  int main(int argc, char **argv)
> > diff --git a/tools/testing/selftests/resctrl/resctrl_val.c
> > b/tools/testing/selftests/resctrl/resctrl_val.c
> > index 51963a6f2186..a9fe61133119 100644
> > --- a/tools/testing/selftests/resctrl/resctrl_val.c
> > +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> > @@ -468,7 +468,9 @@ pid_t bm_pid, ppid;
> >
> >  void ctrlc_handler(int signum, siginfo_t *info, void *ptr)  {
> > -	kill(bm_pid, SIGKILL);
> > +	/* Only kill child after bm_pid is set after fork() */
> > +	if (bm_pid)
> > +		kill(bm_pid, SIGKILL);
> >  	umount_resctrlfs();
> >  	tests_cleanup();
> >  	ksft_print_msg("Ending\n\n");
> > @@ -485,6 +487,8 @@ int signal_handler_register(void)
> >  	struct sigaction sigact;
> >  	int ret = 0;
> >
> > +	bm_pid = 0;
> > +
> 
> Since this is an initialization fix in this area ... what do you think of also
> initializing sigact? It could just be a change to
> 	struct sigaction sigact = {};
> 
> This will prevent registering a signal handler with uninitialized sa_flags.
> 
> Reinette