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

Source file repositories/reference/linux-study-clean/tools/testing/selftests/proc/proc-loadavg-001.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/proc/proc-loadavg-001.c
Extension
.c
Size
1962 bytes
Lines
83
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

#include <errno.h>
#include <sched.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/wait.h>

int main(void)
{
	pid_t pid;
	int wstatus;

	if (unshare(CLONE_NEWPID) == -1) {
		if (errno == ENOSYS || errno == EPERM)
			return 4;
		return 1;
	}

	pid = fork();
	if (pid == -1)
		return 1;
	if (pid == 0) {
		char buf[128], *p;
		int fd;
		ssize_t rv;

		fd = open("/proc/loadavg" , O_RDONLY);
		if (fd == -1)
			return 1;
		rv = read(fd, buf, sizeof(buf));
		if (rv < 3)
			return 1;
		p = buf + rv;

		/* pid 1 */
		if (!(p[-3] == ' ' && p[-2] == '1' && p[-1] == '\n'))
			return 1;

		pid = fork();
		if (pid == -1)
			return 1;
		if (pid == 0)
			return 0;
		if (waitpid(pid, NULL, 0) == -1)
			return 1;

		lseek(fd, 0, SEEK_SET);
		rv = read(fd, buf, sizeof(buf));
		if (rv < 3)
			return 1;
		p = buf + rv;

		/* pid 2 */
		if (!(p[-3] == ' ' && p[-2] == '2' && p[-1] == '\n'))
			return 1;

		return 0;
	}

	if (waitpid(pid, &wstatus, 0) == -1)
		return 1;
	if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0)
		return 0;
	return 1;
}

Annotation

Implementation Notes