Date:   Fri, 10 May 2019 18:37:05 +0100
From:   Andre Przywara <andre.przywara@....com>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "H Peter Anvin" <hpa@...or.com>, "Tony Luck" <tony.luck@...el.com>,
        "Reinette Chatre" <reinette.chatre@...el.com>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>,
        "Xiaochen Shen" <xiaochen.shen@...el.com>,
        "Arshiya Hayatkhan Pathan" <arshiya.hayatkhan.pathan@...el.com>,
        "Sai Praneeth Prakhya" <sai.praneeth.prakhya@...el.com>,
        "Babu Moger" <babu.moger@....com>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        James Morse <James.Morse@....com>
Subject: Re: [PATCH v7 04/13] selftests/resctrl: Add callback to start a
 benchmark

On Sat,  9 Feb 2019 18:50:33 -0800
Fenghua Yu <fenghua.yu@...el.com> wrote:

Hi,

> From: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
> 
> The callback starts a child process and puts the child pid in created
> resctrl group with specified memory bandwidth in schemata. The child
> starts running benchmark.
> 
> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
> Signed-off-by: Arshiya Hayatkhan Pathan <arshiya.hayatkhan.pathan@...el.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
>  tools/testing/selftests/resctrl/resctrl.h     |  27 ++
>  tools/testing/selftests/resctrl/resctrl_val.c | 582 ++++++++++++++++++++++++++
>  2 files changed, 609 insertions(+)
> 
> diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
> index 2e112934d48a..c286790ba24d 100644
> --- a/tools/testing/selftests/resctrl/resctrl.h
> +++ b/tools/testing/selftests/resctrl/resctrl.h
> @@ -3,6 +3,7 @@
>  #ifndef RESCTRL_H
>  #define RESCTRL_H
>  #include <stdio.h>
> +#include <stdarg.h>
>  #include <errno.h>
>  #include <sched.h>
>  #include <stdlib.h>
> @@ -28,10 +29,35 @@
>  		exit(EXIT_FAILURE);		\
>  	} while (0)
>  
> +/*
> + * resctrl_val_param:	resctrl test parameters
> + * @resctrl_val:	Resctrl feature (Eg: mbm, mba.. etc)
> + * @ctrlgrp:		Name of the control monitor group (con_mon grp)
> + * @mongrp:		Name of the monitor group (mon grp)
> + * @cpu_no:		CPU number to which the benchmark would be binded
> + * @span:		Memory bytes accessed in each benchmark iteration
> + * @mum_resctrlfs:	Should the resctrl FS be remounted?
> + * @filename:		Name of file to which the o/p should be written
> + * @bw_report:		Bandwidth report type (reads vs writes)
> + * @setup:		Call back function to setup test environment
> + */
> +struct resctrl_val_param {
> +	char	*resctrl_val;
> +	char	ctrlgrp[64];
> +	char	mongrp[64];
> +	int	cpu_no;
> +	int	span;
> +	int	mum_resctrlfs;
> +	char	filename[64];
> +	char	*bw_report;
> +	int	(*setup)(int num, ...);
> +};
> +
>  pid_t bm_pid, ppid;
>  
>  int remount_resctrlfs(bool mum_resctrlfs);
>  int get_resource_id(int cpu_no, int *resource_id);
> +int umount_resctrlfs(void);
>  int validate_bw_report_request(char *bw_report);
>  int validate_resctrl_feature_request(char *resctrl_val);
>  int taskset_benchmark(pid_t bm_pid, int cpu_no);
> @@ -44,5 +70,6 @@ int perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu,
>  		    int group_fd, unsigned long flags);
>  int run_fill_buf(unsigned long span, int malloc_and_init_memory, int memflush,
>  		 int op, char *resctrl_va);
> +int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param);
>  
>  #endif /* RESCTRL_H */
> diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
> index 2bb317715a2a..43c15e382892 100644
> --- a/tools/testing/selftests/resctrl/resctrl_val.c
> +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> @@ -11,6 +11,7 @@
>   */
>  #include "resctrl.h"
>  
> +#define MB			(1024 * 1024)
>  #define UNCORE_IMC		"uncore_imc"
>  #define READ_FILE_NAME		"events/cas_count_read"
>  #define WRITE_FILE_NAME		"events/cas_count_write"
> @@ -48,6 +49,8 @@ struct imc_counter_config {
>  	int fd;
>  };
>  
> +static char mbm_total_path[1024];
> +static int imcs;
>  static struct imc_counter_config imc_counters_config[MAX_IMCS][2];
>  
>  void membw_initialize_perf_event_attr(int i, int j)
> @@ -116,3 +119,582 @@ void get_event_and_umask(char *cas_count_cfg, int count, bool op)
>  		}
>  	}
>  }
> +
> +static int open_perf_event(int i, int cpu_no, int j)
> +{
> +	imc_counters_config[i][j].fd =
> +		perf_event_open(&imc_counters_config[i][j].pe, -1, cpu_no, -1,
> +				PERF_FLAG_FD_CLOEXEC);
> +
> +	if (imc_counters_config[i][j].fd == -1) {
> +		fprintf(stderr, "Error opening leader %llx\n",
> +			imc_counters_config[i][j].pe.config);
> +
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
> +/* Get type and config (read and write) of an iMC counter */
> +static int read_from_imc_dir(char *imc_dir, int count)
> +{
> +	char cas_count_cfg[1024], imc_counter_cfg[1024], imc_counter_type[1024];
> +	FILE *fp;
> +
> +	/* Get type of iMC counter */
> +	sprintf(imc_counter_type, "%s%s", imc_dir, "type");
> +	fp = fopen(imc_counter_type, "r");
> +	if (!fp) {
> +		perror("Failed to open imc counter type file");
> +
> +		return -1;
> +	}
> +	if (fscanf(fp, "%u", &imc_counters_config[count][READ].type) <= 0) {
> +		perror("Could not get imc type");
> +		fclose(fp);
> +
> +		return -1;
> +	}
> +	fclose(fp);
> +
> +	imc_counters_config[count][WRITE].type =
> +				imc_counters_config[count][READ].type;
> +
> +	/* Get read config */
> +	sprintf(imc_counter_cfg, "%s%s", imc_dir, READ_FILE_NAME);
> +	fp = fopen(imc_counter_cfg, "r");
> +	if (!fp) {
> +		perror("Failed to open imc config file");
> +
> +		return -1;
> +	}
> +	if (fscanf(fp, "%s", cas_count_cfg) <= 0) {
> +		perror("Could not get imc cas count read");
> +		fclose(fp);
> +
> +		return -1;
> +	}
> +	fclose(fp);
> +
> +	get_event_and_umask(cas_count_cfg, count, READ);
> +
> +	/* Get write config */
> +	sprintf(imc_counter_cfg, "%s%s", imc_dir, WRITE_FILE_NAME);
> +	fp = fopen(imc_counter_cfg, "r");
> +	if (!fp) {
> +		perror("Failed to open imc config file");
> +
> +		return -1;
> +	}
> +	if  (fscanf(fp, "%s", cas_count_cfg) <= 0) {
> +		perror("Could not get imc cas count write");
> +		fclose(fp);
> +
> +		return -1;
> +	}
> +	fclose(fp);
> +
> +	get_event_and_umask(cas_count_cfg, count, WRITE);
> +
> +	return 0;
> +}
> +
> +/*
> + * A system can have 'n' number of iMC (Integrated Memory Controller)
> + * counters, get that 'n'. For each iMC counter get it's type and config.
> + * Also, each counter has two configs, one for read and the other for write.
> + * A config again has two parts, event and umask.
> + * Enumerate all these details into an array of structures.
> + *
> + * Return: >= 0 on success. < 0 on failure.
> + */
> +static int num_of_imcs(void)
> +{
> +	unsigned int count = 0;
> +	char imc_dir[1024];
> +	struct dirent *ep;
> +	int ret;
> +	DIR *dp;
> +
> +	dp = opendir(DYN_PMU_PATH);
> +	if (dp) {

Changing this to: if (!dp) {
and handling the error case first makes this more readable and avoids the indentation.

> +		while ((ep = readdir(dp))) {
> +			if (strstr(ep->d_name, UNCORE_IMC)) {
> +				sprintf(imc_dir, "%s/%s/", DYN_PMU_PATH,
> +					ep->d_name);
> +				ret = read_from_imc_dir(imc_dir, count);
> +				if (ret) {
> +					closedir(dp);
> +
> +					return ret;
> +				}
> +				count++;
> +			}
> +		}
> +		closedir(dp);
> +		if (count == 0) {
> +			perror("Unable find iMC counters!\n");
> +
> +			return -1;
> +		}
> +	} else {
> +		perror("Unable to open PMU directory!\n");
> +
> +		return -1;
> +	}
> +
> +	return count;
> +}
> +
> +static int initialize_mem_bw_imc(void)
> +{
> +	int imc, j;
> +
> +	imcs = num_of_imcs();
> +	if (imcs <= 0)
> +		return imcs;
> +
> +	/* Initialize perf_event_attr structures for all iMC's */
> +	for (imc = 0; imc < imcs; imc++) {
> +		for (j = 0; j < 2; j++)
> +			membw_initialize_perf_event_attr(imc, j);
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * get_mem_bw_imc:	Memory band width as reported by iMC counters
> + * @cpu_no:		CPU number that the benchmark PID is binded to
> + * @bw_report:		Bandwidth report type (reads, writes)
> + *
> + * Memory B/W utilized by a process on a socket can be calculated using
> + * iMC counters. Perf events are used to read these counters.
> + *
> + * Return: >= 0 on success. < 0 on failure.
> + */
> +static float get_mem_bw_imc(int cpu_no, char *bw_report)
> +{
> +	float reads, writes, of_mul_read, of_mul_write;
> +	int imc, j, ret;
> +
> +	/* Start all iMC counters to log values (both read and write) */
> +	reads = 0, writes = 0, of_mul_read = 1, of_mul_write = 1;
> +	for (imc = 0; imc < imcs; imc++) {
> +		for (j = 0; j < 2; j++) {
> +			ret = open_perf_event(imc, cpu_no, j);
> +			if (ret)
> +				return -1;
> +		}
> +		for (j = 0; j < 2; j++)
> +			membw_ioctl_perf_event_ioc_reset_enable(imc, j);
> +	}
> +
> +	sleep(1);
> +
> +	/* Stop counters after a second to get results (both read and write) */
> +	for (imc = 0; imc < imcs; imc++) {
> +		for (j = 0; j < 2; j++)
> +			membw_ioctl_perf_event_ioc_disable(imc, j);
> +	}
> +
> +	/*
> +	 * Get results which are stored in struct type imc_counter_config
> +	 * Take over flow into consideration before calculating total b/w
> +	 */
> +	for (imc = 0; imc < imcs; imc++) {
> +		struct imc_counter_config *r =
> +			&imc_counters_config[imc][READ];
> +		struct imc_counter_config *w =
> +			&imc_counters_config[imc][WRITE];
> +
> +		if (read(r->fd, &r->return_value,
> +			 sizeof(struct membw_read_format)) == -1) {
> +			perror("Couldn't get read b/w through iMC");
> +
> +			return -1;
> +		}
> +
> +		if (read(w->fd, &w->return_value,
> +			 sizeof(struct membw_read_format)) == -1) {
> +			perror("Couldn't get write bw through iMC");
> +
> +			return -1;
> +		}
> +
> +		__u64 r_time_enabled = r->return_value.time_enabled;
> +		__u64 r_time_running = r->return_value.time_running;
> +
> +		if (r_time_enabled != r_time_running)
> +			of_mul_read = (float)r_time_enabled /
> +					(float)r_time_running;
> +
> +		__u64 w_time_enabled = w->return_value.time_enabled;
> +		__u64 w_time_running = w->return_value.time_running;
> +
> +		if (w_time_enabled != w_time_running)
> +			of_mul_write = (float)w_time_enabled /
> +					(float)w_time_running;
> +		reads += r->return_value.value * of_mul_read * SCALE;
> +		writes += w->return_value.value * of_mul_write * SCALE;
> +	}
> +
> +	for (imc = 0; imc < imcs; imc++) {
> +		close(imc_counters_config[imc][READ].fd);
> +		close(imc_counters_config[imc][WRITE].fd);
> +	}
> +
> +	if (strcmp(bw_report, "reads") == 0)
> +		return reads;
> +
> +	if (strcmp(bw_report, "writes") == 0)
> +		return writes;
> +
> +	return (reads + writes);
> +}
> +
> +void set_mbm_path(const char *ctrlgrp, const char *mongrp, int resource_id)
> +{
> +	if (ctrlgrp && mongrp)
> +		sprintf(mbm_total_path, CON_MON_MBM_LOCAL_BYTES_PATH,
> +			RESCTRL_PATH, ctrlgrp, mongrp, resource_id);
> +	else if (!ctrlgrp && mongrp)
> +		sprintf(mbm_total_path, MON_MBM_LOCAL_BYTES_PATH, RESCTRL_PATH,
> +			mongrp, resource_id);
> +	else if (ctrlgrp && !mongrp)
> +		sprintf(mbm_total_path, CON_MBM_LOCAL_BYTES_PATH, RESCTRL_PATH,
> +			ctrlgrp, resource_id);
> +	else if (!ctrlgrp && !mongrp)
> +		sprintf(mbm_total_path, MBM_LOCAL_BYTES_PATH, RESCTRL_PATH,
> +			resource_id);
> +}
> +
> +/*
> + * initialize_mem_bw_resctrl:	Appropriately populate "mbm_total_path"
> + * @ctrlgrp:			Name of the control monitor group (con_mon grp)
> + * @mongrp:			Name of the monitor group (mon grp)
> + * @cpu_no:			CPU number that the benchmark PID is binded to
> + * @resctrl_val:		Resctrl feature (Eg: mbm, mba.. etc)
> + */
> +static void initialize_mem_bw_resctrl(const char *ctrlgrp, const char *mongrp,
> +				      int cpu_no, char *resctrl_val)
> +{
> +	int resource_id;
> +
> +	if (get_resource_id(cpu_no, &resource_id) < 0) {
> +		perror("Could not get resource_id");
> +		return;
> +	}
> +
> +	if (strcmp(resctrl_val, "mbm") == 0)
> +		set_mbm_path(ctrlgrp, mongrp, resource_id);
> +
> +	if ((strcmp(resctrl_val, "mba") == 0)) {
> +		if (ctrlgrp)
> +			sprintf(mbm_total_path, CON_MBM_LOCAL_BYTES_PATH,
> +				RESCTRL_PATH, ctrlgrp, resource_id);
> +		else
> +			sprintf(mbm_total_path, MBM_LOCAL_BYTES_PATH,
> +				RESCTRL_PATH, resource_id);
> +	}
> +}
> +
> +/*
> + * Get MBM Local bytes as reported by resctrl FS
> + * For MBM,
> + * 1. If con_mon grp and mon grp are given, then read from con_mon grp's mon grp
> + * 2. If only con_mon grp is given, then read from con_mon grp
> + * 3. If both are not given, then read from root con_mon grp
> + * For MBA,
> + * 1. If con_mon grp is given, then read from it
> + * 2. If con_mon grp is not given, then read from root con_mon grp
> + */
> +static unsigned long get_mem_bw_resctrl(void)
> +{
> +	unsigned long mbm_total = 0;
> +	FILE *fp;
> +
> +	fp = fopen(mbm_total_path, "r");
> +	if (!fp) {
> +		perror("Failed to open total bw file");
> +
> +		return -1;
> +	}
> +	if (fscanf(fp, "%lu", &mbm_total) <= 0) {
> +		perror("Could not get mbm local bytes");
> +		fclose(fp);
> +
> +		return -1;
> +	}
> +	fclose(fp);
> +
> +	return mbm_total;
> +}
> +
> +pid_t bm_pid, ppid;
> +
> +static void ctrlc_handler(int signum, siginfo_t *info, void *ptr)
> +{
> +	kill(bm_pid, SIGKILL);
> +	printf("Ending\n\n");
> +
> +	exit(EXIT_SUCCESS);
> +}
> +
> +/*
> + * print_results_bw:	the memory bandwidth results are stored in a file
> + * @filename:		file that stores the results
> + * @bm_pid:		child pid that runs benchmark
> + * @bw_imc:		perf imc counter value
> + * @bw_resc:		memory bandwidth value
> + *
> + * Return:		0 on success. non-zero on failure.
> + */
> +static int print_results_bw(char *filename,  int bm_pid, float bw_imc,
> +			    unsigned long bw_resc)
> +{
> +	unsigned long diff = labs(bw_imc - bw_resc);

Since bw_imc is float (why, actually?) this should be fabs(). clang
complains about it.

> +	FILE *fp;
> +
> +	if (strcmp(filename, "stdio") == 0 || strcmp(filename, "stderr") == 0) {
> +		printf("Pid: %d \t Mem_BW_iMC: %f \t ", bm_pid, bw_imc);
> +		printf("Mem_BW_resc: %lu \t Difference: %lu\n", bw_resc, diff);
> +	} else {
> +		fp = fopen(filename, "a");
> +		if (!fp) {
> +			perror("Cannot open results file");
> +
> +			return errno;
> +		}
> +		if (fprintf(fp, "Pid: %d \t Mem_BW_iMC: %f \t Mem_BW_resc: %lu \t Difference: %lu\n",
> +			    bm_pid, bw_imc, bw_resc, diff) <= 0) {
> +			fclose(fp);
> +			perror("Could not log results.");
> +
> +			return errno;
> +		}
> +		fclose(fp);
> +	}
> +
> +	return 0;
> +}
> +
> +static int
> +measure_vals(struct resctrl_val_param *param, unsigned long *bw_resc_start)
> +{
> +	unsigned long bw_imc, bw_resc, bw_resc_end;
> +	int ret;
> +
> +	/*
> +	 * Measure memory bandwidth from resctrl and from
> +	 * another source which is perf imc value or could
> +	 * be something else if perf imc event is not available.
> +	 * Compare the two values to validate resctrl value.
> +	 * It takes 1sec to measure the data.
> +	 */
> +	bw_imc = get_mem_bw_imc(param->cpu_no, param->bw_report);
> +	if (bw_imc <= 0)
> +		return bw_imc;
> +
> +	bw_resc_end = get_mem_bw_resctrl();
> +	if (bw_resc_end <= 0)
> +		return bw_resc_end;
> +
> +	bw_resc = (bw_resc_end - *bw_resc_start) / MB;
> +	ret = print_results_bw(param->filename, bm_pid, bw_imc, bw_resc);
> +	if (ret)
> +		return ret;
> +
> +	*bw_resc_start = bw_resc_end;
> +
> +	return 0;
> +}
> +
> +/*
> + * resctrl_val:	execute benchmark and measure memory bandwidth on
> + *			the benchmark
> + * @benchmark_cmd:	benchmark command and its arguments
> + * @param:		parameters passed to resctrl_val()
> + *
> + * Return:		0 on success. non-zero on failure.
> + */
> +int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
> +{
> +	int ret = 0, pipefd[2], pipe_message = 0;

If I get this correctly, we just need to pipe for asynchronous signalling.
So can't we actually use a signal() call here? At least we should make
this pipe_message a single char. This avoids some nasty problems with
read() and write() possibly returning early.

> +	char *resctrl_val = param->resctrl_val;
> +	unsigned long bw_resc_start = 0;
> +	struct sigaction sigact;
> +	union sigval value;
> +	FILE *fp;
> +
> +	if (strcmp(param->filename, "") == 0)
> +		sprintf(param->filename, "stdio");
> +
> +	if (strcmp(param->bw_report, "") == 0)
> +		param->bw_report = "total";
> +
> +	if ((strcmp(resctrl_val, "mba")) == 0 ||
> +	    (strcmp(resctrl_val, "mbm")) == 0) {
> +		ret = validate_bw_report_request(param->bw_report);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = remount_resctrlfs(param->mum_resctrlfs);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * If benchmark wasn't successfully started by child, then child should
> +	 * kill parent, so save parent's pid
> +	 */
> +	ppid = getpid();
> +
> +	/* File based synchronization between parent and child */
> +	fp = fopen("sig", "w");
> +	if (!fp) {
> +		perror("Failed to open sig file");
> +
> +		return -1;
> +	}
> +	if (fprintf(fp, "%d\n", 0) <= 0) {
> +		perror("Unable to establish sync bw parent & child");
> +		fclose(fp);
> +
> +		return -1;
> +	}
> +	fclose(fp);
> +
> +	if (pipe(pipefd)) {
> +		perror("Unable to create pipe");
> +
> +		return -1;
> +	}
> +
> +	/*
> +	 * Fork to start benchmark, save child's pid so that it can be killed
> +	 * when needed
> +	 */
> +	bm_pid = fork();
> +	if (bm_pid == -1) {
> +		perror("Unable to fork");
> +
> +		return -1;
> +	}
> +
> +	if (bm_pid == 0) {
> +		/*
> +		 * Mask all signals except SIGUSR1, parent uses SIGUSR1 to
> +		 * start benchmark
> +		 */
> +		sigfillset(&sigact.sa_mask);
> +		sigdelset(&sigact.sa_mask, SIGUSR1);
> +
> +		sigact.sa_sigaction = run_benchmark;
> +		sigact.sa_flags = SA_SIGINFO;
> +
> +		/* Register for "SIGUSR1" signal from parent */
> +		if (sigaction(SIGUSR1, &sigact, NULL))
> +			PARENT_EXIT("Can't register child for signal");
> +
> +		/* Tell parent that child is ready */
> +		close(pipefd[0]);
> +		pipe_message = 1;
> +		write(pipefd[1], &pipe_message, sizeof(pipe_message));

gcc -O complains about an unchecked return value of write() here.
We could just compare against sizeof(pipe_message) and bail out if it's smaller.

> +		close(pipefd[1]);
> +
> +		/* Suspend child until delivery of "SIGUSR1" from parent */
> +		sigsuspend(&sigact.sa_mask);
> +
> +		PARENT_EXIT("Child is done");
> +	}
> +
> +	printf("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(SIGHUP, &sigact, NULL)) {
> +		perror("Can't register parent for CTRL-C handler");
> +		ret = errno;
> +		goto out;
> +	}
> +
> +	value.sival_ptr = benchmark_cmd;
> +
> +	/* Taskset benchmark to specified cpu */
> +	ret = taskset_benchmark(bm_pid, param->cpu_no);
> +	if (ret)
> +		goto out;
> +
> +	/* 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;
> +
> +	if ((strcmp(resctrl_val, "mbm") == 0) ||
> +	    (strcmp(resctrl_val, "mba") == 0)) {
> +		ret = initialize_mem_bw_imc();
> +		if (ret)
> +			goto out;
> +
> +		initialize_mem_bw_resctrl(param->ctrlgrp, param->mongrp,
> +					  param->cpu_no, resctrl_val);
> +	}
> +
> +	/* Parent waits for child to be ready. */
> +	close(pipefd[1]);
> +	while (pipe_message != 1)
> +		read(pipefd[0], &pipe_message, sizeof(pipe_message));

Same thing with checking the return value here.

Cheers,
Andre.

> +	close(pipefd[0]);
> +
> +	/* Signal child to start benchmark */
> +	if (sigqueue(bm_pid, SIGUSR1, value) == -1) {
> +		perror("Unable to signal child to start execution");
> +		ret = errno;
> +		goto out;
> +	}
> +
> +	/* Give benchmark enough time to fully run */
> +	sleep(1);
> +
> +	/* Test runs until the callback setup() tells the test to stop. */
> +	while (1) {
> +		if (strcmp(resctrl_val, "mbm") == 0) {
> +			ret = param->setup(1, param);
> +			if (ret) {
> +				ret = 0;
> +				break;
> +			}
> +
> +			ret = measure_vals(param, &bw_resc_start);
> +			if (ret)
> +				break;
> +		} else if ((strcmp(resctrl_val, "mba") == 0)) {
> +			ret = param->setup(1, param);
> +			if (ret) {
> +				ret = 0;
> +				break;
> +			}
> +
> +			ret = measure_vals(param, &bw_resc_start);
> +			if (ret)
> +				break;
> +		} else {
> +			break;
> +		}
> +	}
> +
> +out:
> +	kill(bm_pid, SIGKILL);
> +	umount_resctrlfs();
> +
> +	return ret;
> +}

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