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

Source file repositories/reference/linux-study-clean/tools/testing/selftests/proc/proc-uptime-002.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/proc/proc-uptime-002.c
Extension
.c
Size
2483 bytes
Lines
93
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// Test that boottime value in /proc/uptime and CLOCK_BOOTTIME increment
// 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>
#include <unistd.h>
#include <sys/syscall.h>
#include <stdlib.h>
#include <string.h>

#include <stdint.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include "proc-uptime.h"

static inline int sys_sched_getaffinity(pid_t pid, unsigned int len, unsigned long *m)
{
	return syscall(SYS_sched_getaffinity, pid, len, m);
}

static inline int sys_sched_setaffinity(pid_t pid, unsigned int len, unsigned long *m)
{
	return syscall(SYS_sched_setaffinity, pid, len, m);
}

int main(void)
{
	uint64_t u0, u1, c0, c1;
	unsigned int len;
	unsigned long *m;
	unsigned int cpu;
	int fd;

	/* find out "nr_cpu_ids" */
	m = NULL;
	len = 0;
	do {
		len += sizeof(unsigned long);
		free(m);
		m = malloc(len);
	} while (sys_sched_getaffinity(0, len, m) == -1 && errno == EINVAL);

	fd = open("/proc/uptime", O_RDONLY);
	assert(fd >= 0);

	u0 = proc_uptime(fd);
	c0 = clock_boottime();

	for (cpu = 0; cpu < len * 8; cpu++) {
		memset(m, 0, len);
		m[cpu / (8 * sizeof(unsigned long))] |= 1UL << (cpu % (8 * sizeof(unsigned long)));

		/* CPU might not exist, ignore error */
		sys_sched_setaffinity(0, len, m);

		u1 = proc_uptime(fd);
		c1 = clock_boottime();

		/* Is /proc/uptime monotonic ? */
		assert(u1 >= u0);

		/* Is CLOCK_BOOTTIME monotonic ? */
		assert(c1 >= c0);

		/* Is CLOCK_BOOTTIME VS /proc/uptime monotonic ? */
		assert(c0 >= u0);

		u0 = u1;
		c0 = c1;
	}

	return 0;
}

Annotation

Implementation Notes