RE: [PATCH v4 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

Hi Reinette,

On 11/16/2022 5:05 PM, Shaopeng Tan wrote:

...

After creating a child process with fork() in CAT test, if there is an error occurs or such as a SIGINT signal is received, the parent process will be terminated immediately, but the child process will not be killed and also umount_resctrlfs() will not be called.

Add a signal handler like other tests to kill child process, umount resctrlfs, cleanup result files, etc. if an error occurs in parent process. To use ctrlc_handler() of other tests to kill child process(bm_pid), using global bm_pid instead of local bm_pid.

Wait for child process to be killed if an error occurs in child process.

Reviewed-by: Shuah Khan skhan@linuxfoundation.org Signed-off-by: Shaopeng Tan tan.shaopeng@jp.fujitsu.com

---

tools/testing/selftests/resctrl/cat_test.c | 30

++++++++++++++--------

...

1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/resctrl/cat_test.c

b/tools/testing/selftests/resctrl/cat_test.c

...

index 6a8306b0a109..1f8f5cf94e95 100644 --- a/tools/testing/selftests/resctrl/cat_test.c +++ b/tools/testing/selftests/resctrl/cat_test.c @@ -100,10 +100,10 @@ void cat_test_cleanup(void)

int cat_perf_miss_val(int cpu_no, int n, char *cache_type) {

• struct sigaction sigact; unsigned long l_mask, l_mask_1; int ret, pipefd[2], sibling_cpu_no; char pipe_message;

• pid_t bm_pid;

  cache_size = 0;

@@ -181,17 +181,25 @@ 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 {

• /*
  

•  * Register CTRL-C handler for parent, as it has to kill
  

•  * child process before exiting
  

•  */
  

• sigact.sa_sigaction = ctrlc_handler;
  

• sigemptyset(&sigact.sa_mask);
  

• sigact.sa_flags = SA_SIGINFO;
  

• if (sigaction(SIGINT, &sigact, NULL) ||
  

•     sigaction(SIGTERM, &sigact, NULL) ||
  

•     sigaction(SIGHUP, &sigact, NULL))
  

• 	perror("# sigaction");
  

Why keep going at this point?

I tried this change but I was not able to trigger ctrlc_handler(). It

I tested this change using kselftest framework, In this case, the timeout command sent a SIGTERM signal, and then ctrlc_handler() was triggered. Since the handling of SIGINT and SIGHUP signals is overridden in run_fill_buf(), ctrl_handler() may be called if ctrl-c is received.

seems that the handler is changed soon after (see cat_val()->run_fill_buf()) and ctrl_handler() (note the subtle name difference) is run instead when a SIGINT is received. The value of ctrl_handler() is not clear to me though, and it could even be argued that it is broken because it starts with free(startptr) and startptr would likely already be free'd at this point without resetting its value to NULL.

From what I understand ctrl_handler() and its installation from run_fill_buf() could be removed so that it does not override what is being done with this change. Otherwise, from what I can tell, this new handler will never run.

I think removing ctrl_handler() is fine. In CAT test, it overrides ctrlc_handler(). In other tests(CMT,MBA,MBM), the child process used ctrl_handler() to cleanup itself, but the parent process cleanup the child process with ctrlc_handler() properly. Also, avoid using signal(). fill_buf.c：run_fill_buf() 201 /* set up ctrl-c handler */ 202 if (signal(SIGINT, ctrl_handler) == SIG_ERR) 203 printf("Failed to catch SIGINT!\n");

I removed ctrl_handler() and ran resctrl_tests with and without the kselftest framework. There is no problem.

Best regards, Shaopeng Tan