[PATCH v6 0/5] Some improvements of resctrl selftest

[PATCH v6 0/5] Some improvements of resctrl selftest

[Shaopeng Tan]

Hello,

The aim of this patch series is to improve the resctrl selftest.
Without these fixes, some unnecessary processing will be executed
and test results will be confusing. 
There is no behavior change in test themselves.

[patch 1] Make write_schemata() run to set up shemata with 100% allocation
	  on first run in MBM test.
[patch 2] The MBA test result message is always output as "ok",
	  make output message to be "not ok" if MBA check result is failed.
[patch 3] When a child process is created by fork(), the buffer of the 
	  parent process is also copied. Flush the buffer before
	  executing fork().
[patch 4] Add a signal handler to cleanup properly before exiting the 
	  parent process if there is an error occurs after creating 
	  a child process with fork() in the CAT test, and unregister
	  signal handler when each test finished.
[patch 5] Before exiting each test CMT/CAT/MBM/MBA, clear test result 
	  files function cat/cmt/mbm/mba_test_cleanup() are called
	  twice. Delete once.

This patch series is based on Linux v6.2-rc6.

Difference from v5:
[patch 4] 
  - If an error occurs in signal_handler_register() return -1, 
    and if an error occurs in signal_handler_unregister() does 
    not return any value.
  - If signal_handler_register() fails, stop the running
    parents&child process.
  - Ignore the result of signal_handler_unregister() 
    so as not to overwrite earlier value of ret.
  - Fix change log.

Shaopeng Tan (5):
  selftests/resctrl: Fix set up schemata with 100% allocation on first
    run in MBM test
  selftests/resctrl: Return MBA check result and make it to output
    message
  selftests/resctrl: Flush stdout file buffer before executing fork()
  selftests/resctrl: Cleanup properly when an error occurs in CAT test
  selftests/resctrl: Remove duplicate codes that clear each test result
    file

 tools/testing/selftests/resctrl/cat_test.c    | 29 ++++----
 tools/testing/selftests/resctrl/cmt_test.c    |  7 +-
 tools/testing/selftests/resctrl/fill_buf.c    | 14 ----
 tools/testing/selftests/resctrl/mba_test.c    | 23 +++---
 tools/testing/selftests/resctrl/mbm_test.c    | 20 +++---
 tools/testing/selftests/resctrl/resctrl.h     |  2 +
 .../testing/selftests/resctrl/resctrl_tests.c |  4 --
 tools/testing/selftests/resctrl/resctrl_val.c | 71 +++++++++++++------
 tools/testing/selftests/resctrl/resctrlfs.c   |  5 +-
 9 files changed, 98 insertions(+), 77 deletions(-)

-- 
2.27.0

[PATCH v6 1/5] selftests/resctrl: Fix set up schemata with 100% allocation on first run in MBM test

[Shaopeng Tan]

There is a comment "Set up shemata with 100% allocation on the first run"
in function mbm_setup(), but there is an increment bug and the condition
"num_of_runs == 0" will never be met and write_schemata() will never be
called to set schemata to 100%. Even if write_schemata() is called in MBM
test, since it is not supported for MBM test it does not set the schemata.
This is currently fine because resctrl_val_parm->mum_resctrlfs is always 1
and umount/mount will be run in each test to set the schemata to 100%.

To support the usage when MBM test does not unmount/remount resctrl
filesystem before the test starts, fix to call write_schemata() and
set schemata properly when the function is called for the first time.

Also, remove static local variable 'num_of_runs' because this is not
needed as there is resctrl_val_param->num_of_runs which should be used
instead like in cat_setup().

Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
---
 tools/testing/selftests/resctrl/mbm_test.c  | 13 +++++++------
 tools/testing/selftests/resctrl/resctrlfs.c |  4 +++-
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
index 8392e5c55ed0..6d550f012829 100644
--- a/tools/testing/selftests/resctrl/mbm_test.c
+++ b/tools/testing/selftests/resctrl/mbm_test.c
@@ -89,23 +89,24 @@ static int check_results(int span)
 static int mbm_setup(int num, ...)
 {
 	struct resctrl_val_param *p;
-	static int num_of_runs;
 	va_list param;
 	int ret = 0;
 
-	/* Run NUM_OF_RUNS times */
-	if (num_of_runs++ >= NUM_OF_RUNS)
-		return -1;
-
 	va_start(param, num);
 	p = va_arg(param, struct resctrl_val_param *);
 	va_end(param);
 
+	/* Run NUM_OF_RUNS times */
+	if (p->num_of_runs >= NUM_OF_RUNS)
+		return -1;
+
 	/* Set up shemata with 100% allocation on the first run. */
-	if (num_of_runs == 0)
+	if (p->num_of_runs == 0)
 		ret = write_schemata(p->ctrlgrp, "100", p->cpu_no,
 				     p->resctrl_val);
 
+	p->num_of_runs++;
+
 	return ret;
 }
 
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index 6f543e470ad4..8546bc9f1786 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -498,6 +498,7 @@ int write_schemata(char *ctrlgrp, char *schemata, int cpu_no, char *resctrl_val)
 	FILE *fp;
 
 	if (strncmp(resctrl_val, MBA_STR, sizeof(MBA_STR)) &&
+	    strncmp(resctrl_val, MBM_STR, sizeof(MBM_STR)) &&
 	    strncmp(resctrl_val, CAT_STR, sizeof(CAT_STR)) &&
 	    strncmp(resctrl_val, CMT_STR, sizeof(CMT_STR)))
 		return -ENOENT;
@@ -523,7 +524,8 @@ int write_schemata(char *ctrlgrp, char *schemata, int cpu_no, char *resctrl_val)
 	if (!strncmp(resctrl_val, CAT_STR, sizeof(CAT_STR)) ||
 	    !strncmp(resctrl_val, CMT_STR, sizeof(CMT_STR)))
 		sprintf(schema, "%s%d%c%s", "L3:", resource_id, '=', schemata);
-	if (!strncmp(resctrl_val, MBA_STR, sizeof(MBA_STR)))
+	if (!strncmp(resctrl_val, MBA_STR, sizeof(MBA_STR)) ||
+	    !strncmp(resctrl_val, MBM_STR, sizeof(MBM_STR)))
 		sprintf(schema, "%s%d%c%s", "MB:", resource_id, '=', schemata);
 
 	fp = fopen(controlgroup, "w");
-- 
2.27.0

[PATCH v6 2/5] selftests/resctrl: Return MBA check result and make it to output message

[Shaopeng Tan]

Since MBA check result is not returned, the MBA test result message
is always output as "ok" regardless of whether the MBA check result is
true or false.

Make output message to be "not ok" if MBA check result is failed.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
---
 tools/testing/selftests/resctrl/mba_test.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
index 1a1bdb6180cf..e3a473976d74 100644
--- a/tools/testing/selftests/resctrl/mba_test.c
+++ b/tools/testing/selftests/resctrl/mba_test.c
@@ -51,10 +51,10 @@ static int mba_setup(int num, ...)
 	return 0;
 }
 
-static void show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
+static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
 {
 	int allocation, runs;
-	bool failed = false;
+	bool ret = false;
 
 	ksft_print_msg("Results are displayed in (MB)\n");
 	/* Memory bandwidth from 100% down to 10% */
@@ -90,13 +90,15 @@ static void show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
 		ksft_print_msg("avg_bw_imc: %lu\n", avg_bw_imc);
 		ksft_print_msg("avg_bw_resc: %lu\n", avg_bw_resc);
 		if (avg_diff_per > MAX_DIFF_PERCENT)
-			failed = true;
+			ret = true;
 	}
 
 	ksft_print_msg("%s Check schemata change using MBA\n",
-		       failed ? "Fail:" : "Pass:");
-	if (failed)
+		       ret ? "Fail:" : "Pass:");
+	if (ret)
 		ksft_print_msg("At least one test failed\n");
+
+	return ret;
 }
 
 static int check_results(void)
@@ -132,9 +134,7 @@ static int check_results(void)
 
 	fclose(fp);
 
-	show_mba_info(bw_imc, bw_resc);
-
-	return 0;
+	return show_mba_info(bw_imc, bw_resc);
 }
 
 void mba_test_cleanup(void)
-- 
2.27.0

[PATCH v6 3/5] selftests/resctrl: Flush stdout file buffer before executing fork()

[Shaopeng Tan]

When a process has buffered output, a child process created by fork()
will also copy buffered output. When using kselftest framework,
the output (resctrl test result message) will be printed multiple times.

Add fflush() to flush out the buffered output before executing fork().

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
---
 tools/testing/selftests/resctrl/cat_test.c    | 1 +
 tools/testing/selftests/resctrl/resctrl_val.c | 1 +
 tools/testing/selftests/resctrl/resctrlfs.c   | 1 +
 3 files changed, 3 insertions(+)

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index 1c5e90c63254..6a8306b0a109 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -167,6 +167,7 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 		return errno;
 	}
 
+	fflush(stdout);
 	bm_pid = fork();
 
 	/* Set param values for child thread which will be allocated bitmask
diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index b32b96356ec7..6948843bf995 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -629,6 +629,7 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
 	 * Fork to start benchmark, save child's pid so that it can be killed
 	 * when needed
 	 */
+	fflush(stdout);
 	bm_pid = fork();
 	if (bm_pid == -1) {
 		perror("# Unable to fork");
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index 8546bc9f1786..d95688298469 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -678,6 +678,7 @@ int filter_dmesg(void)
 		perror("pipe");
 		return ret;
 	}
+	fflush(stdout);
 	pid = fork();
 	if (pid == 0) {
 		close(pipefds[0]);
-- 
2.27.0

[PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Shaopeng Tan]

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

There is a signal handler registered in CMT/MBM/MBA tests, which kills
child process, unmount resctrlfs, cleanups result files, etc., if a
signal such as SIGINT is received.

Commonize the signal handler registered for CMT/MBM/MBA tests and reuse
it in CAT too.

To reuse the signal handler, make the child process in CAT wait to be
killed by parent process in any case (an error occurred or a signal was
received), and when killing child process use global bm_pid instead of
local bm_pid.

Also, since the MBA/MBA/CMT/CAT are run in order, unregister the signal
handler at the end of each test so that the signal handler cannot be
inherited by other tests.

Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
---
 tools/testing/selftests/resctrl/cat_test.c    | 28 ++++----
 tools/testing/selftests/resctrl/fill_buf.c    | 14 ----
 tools/testing/selftests/resctrl/resctrl.h     |  2 +
 tools/testing/selftests/resctrl/resctrl_val.c | 70 +++++++++++++------
 4 files changed, 68 insertions(+), 46 deletions(-)

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index 6a8306b0a109..3524fa88e3a4 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -103,7 +103,6 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 	unsigned long l_mask, l_mask_1;
 	int ret, pipefd[2], sibling_cpu_no;
 	char pipe_message;
-	pid_t bm_pid;
 
 	cache_size = 0;
 
@@ -181,28 +180,31 @@ 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);
 
 	ret = cat_val(&param);
-	if (ret)
-		return ret;
-
-	ret = check_results(&param);
-	if (ret)
-		return ret;
+	if (ret == 0)
+		ret = check_results(&param);
 
 	if (bm_pid == 0) {
 		/* Tell parent that child is ready */
 		close(pipefd[0]);
 		pipe_message = 1;
 		if (write(pipefd[1], &pipe_message, sizeof(pipe_message)) <
-		    sizeof(pipe_message)) {
-			close(pipefd[1]);
+		    sizeof(pipe_message))
+			/*
+			 * Just print the error message.
+			 * Let while(1) run and wait for itself to be killed.
+			 */
 			perror("# failed signaling parent process");
-			return errno;
-		}
 
 		close(pipefd[1]);
 		while (1)
@@ -222,9 +224,11 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 		kill(bm_pid, SIGKILL);
 	}
 
+	signal_handler_unregister();
+out:
 	cat_test_cleanup();
 	if (bm_pid)
 		umount_resctrlfs();
 
-	return 0;
+	return ret;
 }
diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
index 56ccbeae0638..322c6812e15c 100644
--- a/tools/testing/selftests/resctrl/fill_buf.c
+++ b/tools/testing/selftests/resctrl/fill_buf.c
@@ -33,14 +33,6 @@ static void sb(void)
 #endif
 }
 
-static void ctrl_handler(int signo)
-{
-	free(startptr);
-	printf("\nEnding\n");
-	sb();
-	exit(EXIT_SUCCESS);
-}
-
 static void cl_flush(void *p)
 {
 #if defined(__i386) || defined(__x86_64)
@@ -198,12 +190,6 @@ int run_fill_buf(unsigned long span, int malloc_and_init_memory,
 	unsigned long long cache_size = span;
 	int ret;
 
-	/* set up ctrl-c handler */
-	if (signal(SIGINT, ctrl_handler) == SIG_ERR)
-		printf("Failed to catch SIGINT!\n");
-	if (signal(SIGHUP, ctrl_handler) == SIG_ERR)
-		printf("Failed to catch SIGHUP!\n");
-
 	ret = fill_cache(cache_size, malloc_and_init_memory, memflush, op,
 			 resctrl_val);
 	if (ret) {
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index f0ded31fb3c7..92b59d2f603d 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -107,6 +107,8 @@ void mba_test_cleanup(void);
 int get_cbm_mask(char *cache_type, char *cbm_mask);
 int get_cache_size(int cpu_no, char *cache_type, unsigned long *cache_size);
 void ctrlc_handler(int signum, siginfo_t *info, void *ptr);
+int signal_handler_register(void);
+void signal_handler_unregister(void);
 int cat_val(struct resctrl_val_param *param);
 void cat_test_cleanup(void);
 int cat_perf_miss_val(int cpu_no, int no_of_bits, char *cache_type);
diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index 6948843bf995..c2be2f2505a8 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -476,6 +476,45 @@ void ctrlc_handler(int signum, siginfo_t *info, void *ptr)
 	exit(EXIT_SUCCESS);
 }
 
+/*
+ * Register CTRL-C handler for parent, as it has to kill
+ * child process before exiting
+ */
+int signal_handler_register(void)
+{
+	struct sigaction sigact;
+	int ret = 0;
+
+	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");
+		ret = -1;
+	}
+	return ret;
+}
+
+/*
+ * Reset signal handler to SIG_DFL.
+ * Non-Vaule return because the caller should keep
+ * the error code of other path even if sigaction fails.
+ */
+void signal_handler_unregister(void)
+{
+	struct sigaction sigact;
+
+	sigact.sa_handler = SIG_DFL;
+	sigemptyset(&sigact.sa_mask);
+	if (sigaction(SIGINT, &sigact, NULL) ||
+	    sigaction(SIGTERM, &sigact, NULL) ||
+	    sigaction(SIGHUP, &sigact, NULL)) {
+		perror("# sigaction");
+	}
+}
+
 /*
  * print_results_bw:	the memory bandwidth results are stored in a file
  * @filename:		file that stores the results
@@ -671,39 +710,28 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
 
 	ksft_print_msg("Benchmark PID: %d\n", bm_pid);
 
-	/*
-	 * Register CTRL-C handler for parent, as it has to kill benchmark
-	 * 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");
-		ret = errno;
-		goto out;
-	}
+	ret = signal_handler_register();
+	if (ret)
+		goto out1;
 
 	value.sival_ptr = benchmark_cmd;
 
 	/* Taskset benchmark to specified cpu */
 	ret = taskset_benchmark(bm_pid, param->cpu_no);
 	if (ret)
-		goto out;
+		goto out2;
 
 	/* Write benchmark to specified control&monitoring grp in resctrl FS */
 	ret = write_bm_pid_to_resctrl(bm_pid, param->ctrlgrp, param->mongrp,
 				      resctrl_val);
 	if (ret)
-		goto out;
+		goto out2;
 
 	if (!strncmp(resctrl_val, MBM_STR, sizeof(MBM_STR)) ||
 	    !strncmp(resctrl_val, MBA_STR, sizeof(MBA_STR))) {
 		ret = initialize_mem_bw_imc();
 		if (ret)
-			goto out;
+			goto out2;
 
 		initialize_mem_bw_resctrl(param->ctrlgrp, param->mongrp,
 					  param->cpu_no, resctrl_val);
@@ -718,7 +746,7 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
 		    sizeof(pipe_message)) {
 			perror("# failed reading message from child process");
 			close(pipefd[0]);
-			goto out;
+			goto out2;
 		}
 	}
 	close(pipefd[0]);
@@ -727,7 +755,7 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
 	if (sigqueue(bm_pid, SIGUSR1, value) == -1) {
 		perror("# sigqueue SIGUSR1 to child");
 		ret = errno;
-		goto out;
+		goto out2;
 	}
 
 	/* Give benchmark enough time to fully run */
@@ -761,7 +789,9 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
 		}
 	}
 
-out:
+out2:
+	signal_handler_unregister();
+out1:
 	kill(bm_pid, SIGKILL);
 	umount_resctrlfs();
 
-- 
2.27.0

[PATCH v6 5/5] selftests/resctrl: Remove duplicate codes that clear each test result file

[Shaopeng Tan]

Before exiting each test function(run_cmt/cat/mbm/mba_test()),
test results("ok","not ok") are printed by ksft_test_result() and then
temporary result files are cleaned by function
cmt/cat/mbm/mba_test_cleanup().
However, before running ksft_test_result(),
function cmt/cat/mbm/mba_test_cleanup()
has been run in each test function as follows:
  cmt_resctrl_val()
  cat_perf_miss_val()
  mba_schemata_change()
  mbm_bw_change()

Remove duplicate codes that clear each test result file,
while ensuring cleanup properly even when errors occur in each test.

Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
---
 tools/testing/selftests/resctrl/cmt_test.c      | 7 +++----
 tools/testing/selftests/resctrl/mba_test.c      | 7 +++----
 tools/testing/selftests/resctrl/mbm_test.c      | 7 +++----
 tools/testing/selftests/resctrl/resctrl_tests.c | 4 ----
 4 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c
index 8968e36db99d..617ee95d272d 100644
--- a/tools/testing/selftests/resctrl/cmt_test.c
+++ b/tools/testing/selftests/resctrl/cmt_test.c
@@ -133,13 +133,12 @@ int cmt_resctrl_val(int cpu_no, int n, char **benchmark_cmd)
 
 	ret = resctrl_val(benchmark_cmd, &param);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = check_results(&param, n);
-	if (ret)
-		return ret;
 
+out:
 	cmt_test_cleanup();
 
-	return 0;
+	return ret;
 }
diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
index e3a473976d74..b948938a3b4d 100644
--- a/tools/testing/selftests/resctrl/mba_test.c
+++ b/tools/testing/selftests/resctrl/mba_test.c
@@ -160,13 +160,12 @@ int mba_schemata_change(int cpu_no, char *bw_report, char **benchmark_cmd)
 
 	ret = resctrl_val(benchmark_cmd, &param);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = check_results();
-	if (ret)
-		return ret;
 
+out:
 	mba_test_cleanup();
 
-	return 0;
+	return ret;
 }
diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
index 6d550f012829..040ca1f9c173 100644
--- a/tools/testing/selftests/resctrl/mbm_test.c
+++ b/tools/testing/selftests/resctrl/mbm_test.c
@@ -134,13 +134,12 @@ int mbm_bw_change(int span, int cpu_no, char *bw_report, char **benchmark_cmd)
 
 	ret = resctrl_val(benchmark_cmd, &param);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = check_results(span);
-	if (ret)
-		return ret;
 
+out:
 	mbm_test_cleanup();
 
-	return 0;
+	return ret;
 }
diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
index df0d8d8526fc..8732cf736528 100644
--- a/tools/testing/selftests/resctrl/resctrl_tests.c
+++ b/tools/testing/selftests/resctrl/resctrl_tests.c
@@ -88,7 +88,6 @@ static void run_mbm_test(bool has_ben, char **benchmark_cmd, int span,
 	ksft_test_result(!res, "MBM: bw change\n");
 	if ((get_vendor() == ARCH_INTEL) && res)
 		ksft_print_msg("Intel MBM may be inaccurate when Sub-NUMA Clustering is enabled. Check BIOS configuration.\n");
-	mbm_test_cleanup();
 }
 
 static void run_mba_test(bool has_ben, char **benchmark_cmd, int span,
@@ -107,7 +106,6 @@ static void run_mba_test(bool has_ben, char **benchmark_cmd, int span,
 		sprintf(benchmark_cmd[1], "%d", span);
 	res = mba_schemata_change(cpu_no, bw_report, benchmark_cmd);
 	ksft_test_result(!res, "MBA: schemata change\n");
-	mba_test_cleanup();
 }
 
 static void run_cmt_test(bool has_ben, char **benchmark_cmd, int cpu_no)
@@ -126,7 +124,6 @@ static void run_cmt_test(bool has_ben, char **benchmark_cmd, int cpu_no)
 	ksft_test_result(!res, "CMT: test\n");
 	if ((get_vendor() == ARCH_INTEL) && res)
 		ksft_print_msg("Intel CMT may be inaccurate when Sub-NUMA Clustering is enabled. Check BIOS configuration.\n");
-	cmt_test_cleanup();
 }
 
 static void run_cat_test(int cpu_no, int no_of_bits)
@@ -142,7 +139,6 @@ static void run_cat_test(int cpu_no, int no_of_bits)
 
 	res = cat_perf_miss_val(cpu_no, no_of_bits, "L3");
 	ksft_test_result(!res, "CAT: test\n");
-	cat_test_cleanup();
 }
 
 int main(int argc, char **argv)
-- 
2.27.0

Re: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Reinette Chatre]

Hi Shaopeng,

On 1/30/2023 9:46 PM, Shaopeng Tan wrote:
> After creating a child process with fork() in CAT test, if an error
> occurs or a signal such as SIGINT is received, the parent process will
> be terminated immediately, and therefor the child process will not
> be killed and also resctrlfs is not unmounted.
> 
> There is a signal handler registered in CMT/MBM/MBA tests, which kills
> child process, unmount resctrlfs, cleanups result files, etc., if a
> signal such as SIGINT is received.
> 
> Commonize the signal handler registered for CMT/MBM/MBA tests and reuse
> it in CAT too.
> 
> To reuse the signal handler, make the child process in CAT wait to be
> killed by parent process in any case (an error occurred or a signal was
> received), and when killing child process use global bm_pid instead of
> local bm_pid.
> 
> Also, since the MBA/MBA/CMT/CAT are run in order, unregister the signal
> handler at the end of each test so that the signal handler cannot be
> inherited by other tests.
> 

Great changelog.

...

> @@ -181,28 +180,31 @@ 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);
>  
>  	ret = cat_val(&param);
> -	if (ret)
> -		return ret;
> -
> -	ret = check_results(&param);
> -	if (ret)
> -		return ret;
> +	if (ret == 0)
> +		ret = check_results(&param);
>  
>  	if (bm_pid == 0) {
>  		/* Tell parent that child is ready */
>  		close(pipefd[0]);
>  		pipe_message = 1;
>  		if (write(pipefd[1], &pipe_message, sizeof(pipe_message)) <
> -		    sizeof(pipe_message)) {
> -			close(pipefd[1]);
> +		    sizeof(pipe_message))
> +			/*
> +			 * Just print the error message.
> +			 * Let while(1) run and wait for itself to be killed.
> +			 */
>  			perror("# failed signaling parent process");
> -			return errno;
> -		}
>  
>  		close(pipefd[1]);
>  		while (1)
> @@ -222,9 +224,11 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
>  		kill(bm_pid, SIGKILL);
>  	}
>  
> +	signal_handler_unregister();

I expected the code to be symmetrical but found that the signal
handler is registered by parent, but unregistered by both the parent
and the child.  Could signal_handler_unregister() be moved to the
parent portion of the "if" statement above? 

...

> --- a/tools/testing/selftests/resctrl/resctrl_val.c
> +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> @@ -476,6 +476,45 @@ void ctrlc_handler(int signum, siginfo_t *info, void *ptr)
>  	exit(EXIT_SUCCESS);
>  }
>  
> +/*
> + * Register CTRL-C handler for parent, as it has to kill
> + * child process before exiting
> + */
> +int signal_handler_register(void)
> +{
> +	struct sigaction sigact;
> +	int ret = 0;
> +
> +	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");
> +		ret = -1;
> +	}
> +	return ret;
> +}
> +
> +/*
> + * Reset signal handler to SIG_DFL.
> + * Non-Vaule return because the caller should keep

Typo in "Non-Vaule"

> + * the error code of other path even if sigaction fails.
> + */
> +void signal_handler_unregister(void)
> +{
> +	struct sigaction sigact;
> +
> +	sigact.sa_handler = SIG_DFL;
> +	sigemptyset(&sigact.sa_mask);
> +	if (sigaction(SIGINT, &sigact, NULL) ||
> +	    sigaction(SIGTERM, &sigact, NULL) ||
> +	    sigaction(SIGHUP, &sigact, NULL)) {
> +		perror("# sigaction");
> +	}
> +}
> +
>  /*
>   * print_results_bw:	the memory bandwidth results are stored in a file
>   * @filename:		file that stores the results
> @@ -671,39 +710,28 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
>  
>  	ksft_print_msg("Benchmark PID: %d\n", bm_pid);
>  
> -	/*
> -	 * Register CTRL-C handler for parent, as it has to kill benchmark
> -	 * 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");
> -		ret = errno;
> -		goto out;
> -	}
> +	ret = signal_handler_register();
> +	if (ret)
> +		goto out1;

Please do not use generic "out1" and "out2" goto labels. Could
you please change them to reflect what is done at that exit?
You could keep "out" but "out2" could be renamed to "unregister"
or something more appropriate.

...

> @@ -761,7 +789,9 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
>  		}
>  	}
>  
> -out:
> +out2:
> +	signal_handler_unregister();
> +out1:
>  	kill(bm_pid, SIGKILL);
>  	umount_resctrlfs();
>  

Thank you

Reinette

Re: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Ilpo Järvinen]

On Tue, 31 Jan 2023, Shaopeng Tan wrote:

> After creating a child process with fork() in CAT test, if an error
> occurs or a signal such as SIGINT is received, the parent process will
> be terminated immediately, and therefor the child process will not
> be killed and also resctrlfs is not unmounted.
> 
> There is a signal handler registered in CMT/MBM/MBA tests, which kills
> child process, unmount resctrlfs, cleanups result files, etc., if a
> signal such as SIGINT is received.
>
> Commonize the signal handler registered for CMT/MBM/MBA tests and reuse
> it in CAT too.
> 
> To reuse the signal handler, make the child process in CAT wait to be
> killed by parent process in any case (an error occurred or a signal was
> received), and when killing child process use global bm_pid instead of
> local bm_pid.
> 
> Also, since the MBA/MBA/CMT/CAT are run in order, unregister the signal
> handler at the end of each test so that the signal handler cannot be
> inherited by other tests.
> 
> Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> ---
>  tools/testing/selftests/resctrl/cat_test.c    | 28 ++++----
>  tools/testing/selftests/resctrl/fill_buf.c    | 14 ----
>  tools/testing/selftests/resctrl/resctrl.h     |  2 +
>  tools/testing/selftests/resctrl/resctrl_val.c | 70 +++++++++++++------
>  4 files changed, 68 insertions(+), 46 deletions(-)
> 
> diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
> index 6a8306b0a109..3524fa88e3a4 100644
> --- a/tools/testing/selftests/resctrl/cat_test.c
> +++ b/tools/testing/selftests/resctrl/cat_test.c
> @@ -103,7 +103,6 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
>  	unsigned long l_mask, l_mask_1;
>  	int ret, pipefd[2], sibling_cpu_no;
>  	char pipe_message;
> -	pid_t bm_pid;
>  
>  	cache_size = 0;
>  
> @@ -181,28 +180,31 @@ 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);
>  

>  	ret = cat_val(&param);
> -	if (ret)
> -		return ret;
> -
> -	ret = check_results(&param);
> -	if (ret)
> -		return ret;
> +	if (ret == 0)
> +		ret = check_results(&param);

It would be take this program flow fix out of the signal handler change
into a separate change.

-- 
 i.

RE: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Shaopeng Tan (Fujitsu)]

Hi Ilpo,

> On Tue, 31 Jan 2023, Shaopeng Tan wrote:
> 
> > After creating a child process with fork() in CAT test, if an error
> > occurs or a signal such as SIGINT is received, the parent process will
> > be terminated immediately, and therefor the child process will not be
> > killed and also resctrlfs is not unmounted.
> >
> > There is a signal handler registered in CMT/MBM/MBA tests, which kills
> > child process, unmount resctrlfs, cleanups result files, etc., if a
> > signal such as SIGINT is received.
> >
> > Commonize the signal handler registered for CMT/MBM/MBA tests and
> > reuse it in CAT too.
> >
> > To reuse the signal handler, make the child process in CAT wait to be
> > killed by parent process in any case (an error occurred or a signal
> > was received), and when killing child process use global bm_pid
> > instead of local bm_pid.
> >
> > Also, since the MBA/MBA/CMT/CAT are run in order, unregister the
> > signal handler at the end of each test so that the signal handler
> > cannot be inherited by other tests.
> >
> > Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> > ---
> >  tools/testing/selftests/resctrl/cat_test.c    | 28 ++++----
> >  tools/testing/selftests/resctrl/fill_buf.c    | 14 ----
> >  tools/testing/selftests/resctrl/resctrl.h     |  2 +
> >  tools/testing/selftests/resctrl/resctrl_val.c | 70
> > +++++++++++++------
> >  4 files changed, 68 insertions(+), 46 deletions(-)
> >
> > diff --git a/tools/testing/selftests/resctrl/cat_test.c
> > b/tools/testing/selftests/resctrl/cat_test.c
> > index 6a8306b0a109..3524fa88e3a4 100644
> > --- a/tools/testing/selftests/resctrl/cat_test.c
> > +++ b/tools/testing/selftests/resctrl/cat_test.c
> > @@ -103,7 +103,6 @@ int cat_perf_miss_val(int cpu_no, int n, char
> *cache_type)
> >  	unsigned long l_mask, l_mask_1;
> >  	int ret, pipefd[2], sibling_cpu_no;
> >  	char pipe_message;
> > -	pid_t bm_pid;
> >
> >  	cache_size = 0;
> >
> > @@ -181,28 +180,31 @@ 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);
> >
> 
> >  	ret = cat_val(&param);
> > -	if (ret)
> > -		return ret;
> > -
> > -	ret = check_results(&param);
> > -	if (ret)
> > -		return ret;
> > +	if (ret == 0)
> > +		ret = check_results(&param);
> 
> It would be take this program flow fix out of the signal handler change into a
> separate change.

Do you mean this fix should be separated into two patches?

To make the child process wait to be killed by parent process
in any case(an error occurred or a signal was received),
I fixed it like this.

This fix was discussed here.
https://lore.kernel.org/lkml/2ab9ca20-c757-7dd8-b770-2b84d171cbfb@intel.com/

Best regards,
Shaopeng TAN

RE: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Ilpo Järvinen]

On Tue, 7 Feb 2023, Shaopeng Tan (Fujitsu) wrote:

> > On Tue, 31 Jan 2023, Shaopeng Tan wrote:
> > 
> > > After creating a child process with fork() in CAT test, if an error
> > > occurs or a signal such as SIGINT is received, the parent process will
> > > be terminated immediately, and therefor the child process will not be
> > > killed and also resctrlfs is not unmounted.
> > >
> > > There is a signal handler registered in CMT/MBM/MBA tests, which kills
> > > child process, unmount resctrlfs, cleanups result files, etc., if a
> > > signal such as SIGINT is received.
> > >
> > > Commonize the signal handler registered for CMT/MBM/MBA tests and
> > > reuse it in CAT too.
> > >
> > > To reuse the signal handler, make the child process in CAT wait to be
> > > killed by parent process in any case (an error occurred or a signal
> > > was received), and when killing child process use global bm_pid
> > > instead of local bm_pid.
> > >
> > > Also, since the MBA/MBA/CMT/CAT are run in order, unregister the
> > > signal handler at the end of each test so that the signal handler
> > > cannot be inherited by other tests.
> > >
> > > Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> > > ---

> > >  	ret = cat_val(&param);
> > > -	if (ret)
> > > -		return ret;
> > > -
> > > -	ret = check_results(&param);
> > > -	if (ret)
> > > -		return ret;
> > > +	if (ret == 0)
> > > +		ret = check_results(&param);
> > 
> > It would be take this program flow fix out of the signal handler change into a
> > separate change.
> 
> Do you mean this fix should be separated into two patches?

Yes.

Currently, I see your patch doing (mainly) two things:
1) cleaning up the messy signal handler logic
2) fixing the early return in case of error from cat_val() or 
   check_results()

Both are good changes and both are needed to fully fix things. But (IMHO) 
those are indepedent enough that it would warrant to split this change 
into two.

-- 
 i.

> To make the child process wait to be killed by parent process
> in any case(an error occurred or a signal was received),
> I fixed it like this.
> 
> This fix was discussed here.
> https://lore.kernel.org/lkml/2ab9ca20-c757-7dd8-b770-2b84d171cbfb@intel.com/

Re: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Ilpo Järvinen]

On Tue, 31 Jan 2023, Shaopeng Tan wrote:

> After creating a child process with fork() in CAT test, if an error
> occurs or a signal such as SIGINT is received, the parent process will
> be terminated immediately, and therefor the child process will not
> be killed and also resctrlfs is not unmounted.
> 
> There is a signal handler registered in CMT/MBM/MBA tests, which kills
> child process, unmount resctrlfs, cleanups result files, etc., if a
> signal such as SIGINT is received.
> 
> Commonize the signal handler registered for CMT/MBM/MBA tests and reuse
> it in CAT too.
> 
> To reuse the signal handler, make the child process in CAT wait to be
> killed by parent process in any case (an error occurred or a signal was
> received), and when killing child process use global bm_pid instead of
> local bm_pid.
> 
> Also, since the MBA/MBA/CMT/CAT are run in order, unregister the signal
> handler at the end of each test so that the signal handler cannot be
> inherited by other tests.
> 
> Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> ---

>  	if (bm_pid == 0) {
>  		/* Tell parent that child is ready */
>  		close(pipefd[0]);
>  		pipe_message = 1;
>  		if (write(pipefd[1], &pipe_message, sizeof(pipe_message)) <
> -		    sizeof(pipe_message)) {
> -			close(pipefd[1]);
> +		    sizeof(pipe_message))
> +			/*
> +			 * Just print the error message.
> +			 * Let while(1) run and wait for itself to be killed.
> +			 */
>  			perror("# failed signaling parent process");

If the write error is ignored here, won't it just lead to parent hanging 
forever waiting for the child to send the message through the pipe which 
will never come?


-- 
 i.

RE: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Shaopeng Tan (Fujitsu)]

Hi Ilpo,

> On Tue, 31 Jan 2023, Shaopeng Tan wrote:
> 
> > After creating a child process with fork() in CAT test, if an error
> > occurs or a signal such as SIGINT is received, the parent process will
> > be terminated immediately, and therefor the child process will not be
> > killed and also resctrlfs is not unmounted.
> >
> > There is a signal handler registered in CMT/MBM/MBA tests, which kills
> > child process, unmount resctrlfs, cleanups result files, etc., if a
> > signal such as SIGINT is received.
> >
> > Commonize the signal handler registered for CMT/MBM/MBA tests and
> > reuse it in CAT too.
> >
> > To reuse the signal handler, make the child process in CAT wait to be
> > killed by parent process in any case (an error occurred or a signal
> > was received), and when killing child process use global bm_pid
> > instead of local bm_pid.
> >
> > Also, since the MBA/MBA/CMT/CAT are run in order, unregister the
> > signal handler at the end of each test so that the signal handler
> > cannot be inherited by other tests.
> >
> > Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> > ---
> 
> >  	if (bm_pid == 0) {
> >  		/* Tell parent that child is ready */
> >  		close(pipefd[0]);
> >  		pipe_message = 1;
> >  		if (write(pipefd[1], &pipe_message, sizeof(pipe_message)) <
> > -		    sizeof(pipe_message)) {
> > -			close(pipefd[1]);
> > +		    sizeof(pipe_message))
> > +			/*
> > +			 * Just print the error message.
> > +			 * Let while(1) run and wait for itself to be killed.
> > +			 */
> >  			perror("# failed signaling parent process");
> 
> If the write error is ignored here, won't it just lead to parent hanging forever
> waiting for the child to send the message through the pipe which will never
> come?

If the write error is ignored here, the pipe will be closed by "close(pipefd[1]);" and child process will wait to be killed by "while(1)".
---
-			return errno;
-		}

 		close(pipefd[1]);
 		while (1)
---

If all file descriptors referring to the write end of a pipe have been closed, 
then an attempt to read(2) from the pipe will see end-of-file (read(2) will return 0).
Then, "perror("# failed reading from child process");" occurs.
---
        } else {
                /* Parent waits for child to be ready. */
                close(pipefd[1]);
                pipe_message = 0;
                while (pipe_message != 1) {
                        if (read(pipefd[0], &pipe_message,
                                 sizeof(pipe_message)) < sizeof(pipe_message)) {
                                perror("# failed reading from child process");
                                break;
                        }
                }
                close(pipefd[0]);
                kill(bm_pid, SIGKILL);
                signal_handler_unregister();
        }
---

Best regards,
Shaopeng TAN

RE: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Shaopeng Tan (Fujitsu)]

Hi Ilpo,

> On Tue, 7 Feb 2023, Shaopeng Tan (Fujitsu) wrote:
> 
> > > On Tue, 31 Jan 2023, Shaopeng Tan wrote:
> > >
> > > > After creating a child process with fork() in CAT test, if an
> > > > error occurs or a signal such as SIGINT is received, the parent
> > > > process will be terminated immediately, and therefor the child
> > > > process will not be killed and also resctrlfs is not unmounted.
> > > >
> > > > There is a signal handler registered in CMT/MBM/MBA tests, which
> > > > kills child process, unmount resctrlfs, cleanups result files,
> > > > etc., if a signal such as SIGINT is received.
> > > >
> > > > Commonize the signal handler registered for CMT/MBM/MBA tests and
> > > > reuse it in CAT too.
> > > >
> > > > To reuse the signal handler, make the child process in CAT wait to
> > > > be killed by parent process in any case (an error occurred or a
> > > > signal was received), and when killing child process use global
> > > > bm_pid instead of local bm_pid.
> > > >
> > > > Also, since the MBA/MBA/CMT/CAT are run in order, unregister the
> > > > signal handler at the end of each test so that the signal handler
> > > > cannot be inherited by other tests.
> > > >
> > > > Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> > > > ---
> 
> > > >  	ret = cat_val(&param);
> > > > -	if (ret)
> > > > -		return ret;
> > > > -
> > > > -	ret = check_results(&param);
> > > > -	if (ret)
> > > > -		return ret;
> > > > +	if (ret == 0)
> > > > +		ret = check_results(&param);
> > >
> > > It would be take this program flow fix out of the signal handler
> > > change into a separate change.
> >
> > Do you mean this fix should be separated into two patches?
> 
> Yes.
> 
> Currently, I see your patch doing (mainly) two things:
> 1) cleaning up the messy signal handler logic
> 2) fixing the early return in case of error from cat_val() or
>    check_results()
> 
> Both are good changes and both are needed to fully fix things. But (IMHO)
> those are indepedent enough that it would warrant to split this change into two.

Thanks for your advice, I will split it in next version


Best regards,
Shaopeng TAN

RE: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

[Ilpo Järvinen]

On Wed, 8 Feb 2023, Shaopeng Tan (Fujitsu) wrote:
> > On Tue, 31 Jan 2023, Shaopeng Tan wrote:
> > 
> > > After creating a child process with fork() in CAT test, if an error
> > > occurs or a signal such as SIGINT is received, the parent process will
> > > be terminated immediately, and therefor the child process will not be
> > > killed and also resctrlfs is not unmounted.
> > >
> > > There is a signal handler registered in CMT/MBM/MBA tests, which kills
> > > child process, unmount resctrlfs, cleanups result files, etc., if a
> > > signal such as SIGINT is received.
> > >
> > > Commonize the signal handler registered for CMT/MBM/MBA tests and
> > > reuse it in CAT too.
> > >
> > > To reuse the signal handler, make the child process in CAT wait to be
> > > killed by parent process in any case (an error occurred or a signal
> > > was received), and when killing child process use global bm_pid
> > > instead of local bm_pid.
> > >
> > > Also, since the MBA/MBA/CMT/CAT are run in order, unregister the
> > > signal handler at the end of each test so that the signal handler
> > > cannot be inherited by other tests.
> > >
> > > Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> > > ---
> > 
> > >  	if (bm_pid == 0) {
> > >  		/* Tell parent that child is ready */
> > >  		close(pipefd[0]);
> > >  		pipe_message = 1;
> > >  		if (write(pipefd[1], &pipe_message, sizeof(pipe_message)) <
> > > -		    sizeof(pipe_message)) {
> > > -			close(pipefd[1]);
> > > +		    sizeof(pipe_message))
> > > +			/*
> > > +			 * Just print the error message.
> > > +			 * Let while(1) run and wait for itself to be killed.
> > > +			 */
> > >  			perror("# failed signaling parent process");
> > 
> > If the write error is ignored here, won't it just lead to parent hanging forever
> > waiting for the child to send the message through the pipe which will never
> > come?
> 
> If the write error is ignored here, the pipe will be closed by "close(pipefd[1]);" and child process will wait to be killed by "while(1)".
> ---
> -			return errno;
> -		}
> 
>  		close(pipefd[1]);
>  		while (1)
> ---
> 
> If all file descriptors referring to the write end of a pipe have been closed, 
> then an attempt to read(2) from the pipe will see end-of-file (read(2) will return 0).
> Then, "perror("# failed reading from child process");" occurs.
> ---
>         } else {
>                 /* Parent waits for child to be ready. */
>                 close(pipefd[1]);
>                 pipe_message = 0;
>                 while (pipe_message != 1) {
>                         if (read(pipefd[0], &pipe_message,
>                                  sizeof(pipe_message)) < sizeof(pipe_message)) {
>                                 perror("# failed reading from child process");
>                                 break;
>                         }
>                 }
>                 close(pipefd[0]);
>                 kill(bm_pid, SIGKILL);
>                 signal_handler_unregister();
>         }

Ah, indeed read() will pick up the close event. So your code seem fine 
after all.

-- 
 i.