Subject: Re: [PATCH V2 06/12] selftests, powerpc: Add test for system wide DSCR default

From: Shuah Khan <[email-masked]>
Date: Tue, 13 Jan 2015 08:22:55 -0700

On 01/13/2015 03:22 AM, Anshuman Khandual wrote:
> This patch adds a test case for the system wide DSCR default
> value, which when changed through it's sysfs interface must
> be visible to all threads reading DSCR either through the
> privilege state SPR or the problem state SPR. The DSCR value
> change should be immediate as well.
> 
> Signed-off-by: Anshuman Khandual <[email-masked]>
> ---
>  tools/testing/selftests/powerpc/Makefile           |   2 +-
>  tools/testing/selftests/powerpc/dscr/Makefile      |  17 +++
>  tools/testing/selftests/powerpc/dscr/dscr.h        | 120 ++++++++++++++++++++
>  .../selftests/powerpc/dscr/dscr_default_test.c     | 121 +++++++++++++++++++++
>  4 files changed, 259 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/powerpc/dscr/Makefile
>  create mode 100644 tools/testing/selftests/powerpc/dscr/dscr.h
>  create mode 100644 tools/testing/selftests/powerpc/dscr/dscr_default_test.c
> 
> diff --git a/tools/testing/selftests/powerpc/Makefile b/tools/testing/selftests/powerpc/Makefile
> index f6ff90a..1318883 100644
> --- a/tools/testing/selftests/powerpc/Makefile
> +++ b/tools/testing/selftests/powerpc/Makefile
> @@ -13,7 +13,7 @@ CFLAGS := -Wall -O2 -flto -Wall -Werror -DGIT_VERSION='"$(GIT_VERSION)"' -I$(CUR
>  
>  export CC CFLAGS
>  
> -TARGETS = pmu copyloops mm tm primitives
> +TARGETS = pmu copyloops mm tm primitives dscr
>  
>  endif
>  
> diff --git a/tools/testing/selftests/powerpc/dscr/Makefile b/tools/testing/selftests/powerpc/dscr/Makefile
> new file mode 100644
> index 0000000..0aa90ab
> --- /dev/null
> +++ b/tools/testing/selftests/powerpc/dscr/Makefile
> @@ -0,0 +1,17 @@
> +PROGS := dscr_default_test
> +
> +CFLAGS := $(CFLAGS) -lpthread
> +
> +all: $(PROGS)
> +
> +$(PROGS): ../harness.c
> +
> +run_tests: all
> +	@-for PROG in $(PROGS); do \
> +		./$$PROG; \
> +	done;
> +
> +clean:
> +	rm -f $(PROGS) *.o
> +
> +.PHONY: all run_tests clean
> diff --git a/tools/testing/selftests/powerpc/dscr/dscr.h b/tools/testing/selftests/powerpc/dscr/dscr.h
> new file mode 100644
> index 0000000..2e6535b
> --- /dev/null
> +++ b/tools/testing/selftests/powerpc/dscr/dscr.h
> @@ -0,0 +1,120 @@
> +/*
> + * POWER Data Stream Control Register (DSCR)
> + *
> + * This header file contains helper functions and macros
> + * required for all the DSCR related test cases.
> + *
> + * Copyright (C) 2012 Anton Blanchard <[email-masked]>, IBM
> + * Copyright (C) 2015 Anshuman Khandual <[email-masked]>, IBM
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +#ifndef _SELFTESTS_POWERPC_DSCR_DSCR_H
> +#define _SELFTESTS_POWERPC_DSCR_DSCR_H
> +
> +#include <unistd.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <fcntl.h>
> +#include <dirent.h>
> +#include <pthread.h>
> +#include <sched.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <sys/wait.h>
> +
> +#include "utils.h"
> +
> +#define SPRN_DSCR	0x11	/* Privilege state SPR */
> +#define SPRN_DSCR_USR	0x03	/* Problem state SPR */
> +#define THREADS		100	/* Max threads */
> +#define COUNT		100	/* Max iterations */
> +#define DSCR_MAX	16	/* Max DSCR value */
> +#define LEN_MAX		100	/* Max name length */
> +
> +#define DSCR_DEFAULT	"/sys/devices/system/cpu/dscr_default"
> +#define CPU_PATH	"/sys/devices/system/cpu/"
> +
> +#define rmb()  asm volatile("lwsync":::"memory")
> +#define wmb()  asm volatile("lwsync":::"memory")
> +
> +#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
> +
> +/* Prilvilege state DSCR access */
> +inline unsigned long get_dscr(void)
> +{
> +	unsigned long ret;
> +
> +	asm volatile("mfspr %0,%1" : "=r" (ret): "i" (SPRN_DSCR));
> +
> +	return ret;
> +}
> +
> +inline void set_dscr(unsigned long val)
> +{
> +	asm volatile("mtspr %1,%0" : : "r" (val), "i" (SPRN_DSCR));
> +}
> +
> +/* Problem state DSCR access */
> +inline unsigned long get_dscr_usr(void)
> +{
> +	unsigned long ret;
> +
> +	asm volatile("mfspr %0,%1" : "=r" (ret): "i" (SPRN_DSCR_USR));
> +
> +	return ret;
> +}
> +
> +inline void set_dscr_usr(unsigned long val)
> +{
> +	asm volatile("mtspr %1,%0" : : "r" (val), "i" (SPRN_DSCR_USR));
> +}
> +
> +/* Default DSCR access */
> +unsigned long get_default_dscr(void)
> +{
> +	int fd = -1;
> +	char buf[16];
> +	unsigned long val;
> +
> +	if (fd == -1) {
> +		fd = open(DSCR_DEFAULT, O_RDONLY);
> +		if (fd == -1) {
> +			perror("open() failed\n");
> +			exit(1);
> +		}
> +	}
> +	memset(buf, 0, sizeof(buf));
> +	lseek(fd, 0, SEEK_SET);
> +	read(fd, buf, sizeof(buf));
> +	sscanf(buf, "%lx", &val);
> +	close(fd);
> +	return val;
> +}
> +
> +void set_default_dscr(unsigned long val)
> +{
> +	int fd = -1;
> +	char buf[16];
> +
> +	if (fd == -1) {
> +		fd = open(DSCR_DEFAULT, O_RDWR);
> +		if (fd == -1) {
> +			perror("open() failed\n");
> +			exit(1);
> +		}
> +	}
> +	sprintf(buf, "%lx\n", val);
> +	write(fd, buf, strlen(buf));
> +	close(fd);
> +}
> +
> +double uniform_deviate(int seed)
> +{
> +	return seed * (1.0 / (RAND_MAX + 1.0));
> +}
> +#endif	/* _SELFTESTS_POWERPC_DSCR_DSCR_H */
> diff --git a/tools/testing/selftests/powerpc/dscr/dscr_default_test.c b/tools/testing/selftests/powerpc/dscr/dscr_default_test.c
> new file mode 100644
> index 0000000..fd8b7b9
> --- /dev/null
> +++ b/tools/testing/selftests/powerpc/dscr/dscr_default_test.c
> @@ -0,0 +1,121 @@
> +/*
> + * POWER Data Stream Control Register (DSCR) default test
> + *
> + * This test modifies the system wide default DSCR through
> + * it's sysfs interface and then verifies that all threads
> + * see the correct changed DSCR value immediately.
> + *
> + * Copyright (C) 2012 Anton Blanchard <[email-masked]>, IBM
> + * Copyright (C) 2015 Anshuman Khandual <[email-masked]>, IBM
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +#include "dscr.h"
> +
> +static unsigned long dscr;		/* System DSCR default */
> +static unsigned long sequence;
> +static unsigned long result[THREADS];
> +
> +static void *do_test(void *in)
> +{
> +	unsigned long thread = (unsigned long)in;
> +	unsigned long i;
> +
> +	for (i = 0; i < COUNT; i++) {
> +		unsigned long d, cur_dscr, cur_dscr_usr;
> +		unsigned long s1, s2;
> +
> +		s1 = ACCESS_ONCE(sequence);
> +		if (s1 & 1)
> +			continue;
> +		rmb();
> +
> +		d = dscr;
> +		cur_dscr = get_dscr();
> +		cur_dscr_usr = get_dscr_usr();
> +
> +		rmb();
> +		s2 = sequence;
> +
> +		if (s1 != s2)
> +			continue;
> +
> +		if (cur_dscr != d) {
> +			fprintf(stderr, "thread %ld kernel DSCR should be %ld "
> +				"but is %ld\n", thread, d, cur_dscr);
> +			result[thread] = 1;
> +			pthread_exit(&result[thread]);
> +		}
> +
> +		if (cur_dscr_usr != d) {
> +			fprintf(stderr, "thread %ld user DSCR should be %ld "
> +				"but is %ld\n", thread, d, cur_dscr_usr);
> +			result[thread] = 1;
> +			pthread_exit(&result[thread]);
> +		}
> +	}
> +	result[thread] = 0;
> +	pthread_exit(&result[thread]);
> +}
> +
> +int test_body(void)
> +{
> +	pthread_t threads[THREADS];
> +	unsigned long i, *status[THREADS];
> +
> +	/* Initial DSCR default */
> +	dscr = 1;
> +	set_default_dscr(dscr);
> +
> +	/* Spawn all testing threads */
> +	for (i = 0; i < THREADS; i++) {
> +		if (pthread_create(&threads[i], NULL, do_test, (void *)i)) {
> +			perror("pthread_create() failed\n");
> +			exit(1);
> +		}
> +	}
> +
> +	srand(getpid());
> +
> +	/* Keep changing the DSCR default */
> +	for (i = 0; i < COUNT; i++) {
> +		double ret = uniform_deviate(rand());
> +
> +		if (ret < 0.0001) {
> +			sequence++;
> +			wmb();
> +
> +			dscr++;
> +			if (dscr > DSCR_MAX)
> +				dscr = 0;
> +
> +			set_default_dscr(dscr);
> +
> +			wmb();
> +			sequence++;
> +		}
> +	}
> +
> +	/* Individual testing thread exit status */
> +	for (i = 0; i < THREADS; i++) {
> +		if (pthread_join(threads[i], (void **)&(status[i]))) {
> +			perror("pthread_join() failed\n");
> +			exit(1);
> +		}
> +
> +		if (*status[i]) {
> +			printf("%ldth thread failed to join with %ld status\n",
> +								i, *status[i]);
> +			return 1;
> +		}
> +	}
> +	return 0;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	return test_harness(test_body, "dscr_default_test");
> +}
> 

Could you please add a .gitignore for powerpc targets as we
discussed earlier. It can be separate patch.

Also, I would like to see the test results reports using
kselftest.h - it can be separate patch in the interest of
getting tests in.

Acked-by: Shuah Khan <[email-masked]>

Please take this through powerpc maintainer git.

thanks,
-- Shuah

-- 
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
[email-masked] | (970) 217-8978