Commit 270b2a67 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Thomas Gleixner
Browse files

selftests/proc: Remove idle time monotonicity assertions 



Due to broken iowait task counting design (cf: comments above
get_cpu_idle_time_us() and nr_iowait()), it is not possible to provide
the guarantee that /proc/stat or /proc/uptime display monotonic idle
time values.

Remove the assertions that verify the related wrong assumption so that
testers and maintainers don't spend more time on that.

Reported-by: default avatarYu Liao <liaoyu15@huawei.com>
Reported-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230222144649.624380-8-frederic@kernel.org
parent 9a1d4b8a

tools/testing/selftests/proc/proc-uptime-001.c

+6 −6
Original line number Diff line number Diff line
@@ -13,7 +13,9 @@ 
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

// Test that values in /proc/uptime increment monotonically.

// Test that boottime value in /proc/uptime increments monotonically.

// We don't test idle time monotonicity due to broken iowait task

// counting, cf: comment above get_cpu_idle_time_us()

#undef NDEBUG

#include <assert.h>

#include <stdint.h>
@@ -25,20 +27,18 @@ 


int main(void)

{

	uint64_t start, u0, u1, i0, i1;

	uint64_t start, u0, u1;

	int fd;



	fd = open("/proc/uptime", O_RDONLY);

	assert(fd >= 0);



	proc_uptime(fd, &u0, &i0);

	u0 = proc_uptime(fd);

	start = u0;

	do {

		proc_uptime(fd, &u1, &i1);

		u1 = proc_uptime(fd);

		assert(u1 >= u0);

		assert(i1 >= i0);

		u0 = u1;

		i0 = i1;

	} while (u1 - start < 100);



	return 0;

tools/testing/selftests/proc/proc-uptime-002.c

+6 −7
Original line number Diff line number Diff line
@@ -13,8 +13,9 @@ 
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

// Test that values in /proc/uptime increment monotonically

// while shifting across CPUs.

// Test that boottime value in /proc/uptime increments monotonically

// while shifting across CPUs. We don't test idle time monotonicity

// due to broken iowait task counting, cf: comment above get_cpu_idle_time_us()

#undef NDEBUG

#include <assert.h>

#include <errno.h>
@@ -45,7 +46,7 @@ int main(void) 
	unsigned int len;

	unsigned long *m;

	unsigned int cpu;

	uint64_t u0, u1, i0, i1;

	uint64_t u0, u1;

	int fd;



	/* find out "nr_cpu_ids" */
@@ -60,7 +61,7 @@ int main(void) 
	fd = open("/proc/uptime", O_RDONLY);

	assert(fd >= 0);



	proc_uptime(fd, &u0, &i0);

	u0 = proc_uptime(fd);

	for (cpu = 0; cpu < len * 8; cpu++) {

		memset(m, 0, len);

		m[cpu / (8 * sizeof(unsigned long))] |= 1UL << (cpu % (8 * sizeof(unsigned long)));
@@ -68,11 +69,9 @@ int main(void) 
		/* CPU might not exist, ignore error */

		sys_sched_setaffinity(0, len, m);



		proc_uptime(fd, &u1, &i1);

		u1 = proc_uptime(fd);

		assert(u1 >= u0);

		assert(i1 >= i0);

		u0 = u1;

		i0 = i1;

	}



	return 0;

tools/testing/selftests/proc/proc-uptime.h

+2 −14
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ 


#include "proc.h"



static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)

static uint64_t proc_uptime(int fd)

{

	uint64_t val1, val2;

	char buf[64], *p;
@@ -43,18 +43,6 @@ static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle) 
	assert(p[3] == ' ');



	val2 = (p[1] - '0') * 10 + p[2] - '0';

	*uptime = val1 * 100 + val2;



	p += 4;



	val1 = xstrtoull(p, &p);

	assert(p[0] == '.');

	assert('0' <= p[1] && p[1] <= '9');

	assert('0' <= p[2] && p[2] <= '9');

	assert(p[3] == '\n');



	val2 = (p[1] - '0') * 10 + p[2] - '0';

	*idle = val1 * 100 + val2;



	assert(p + 4 == buf + rv);

	return val1 * 100 + val2;

}