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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (c) 2024 Meta Platforms, Inc. and affiliates.
* Copyright (c) 2024 David Vernet <dvernet@meta.com>
*/
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <unistd.h>
#include <zlib.h>
#include "util.h"
#ifndef SCHED_EXT
#define SCHED_EXT 7
#endif
/* Returns read len on success, or -errno on failure. */
static ssize_t read_text(const char *path, char *buf, size_t max_len)
{
ssize_t len;
int fd;
fd = open(path, O_RDONLY);
if (fd < 0)
return -errno;
len = read(fd, buf, max_len - 1);
if (len >= 0)
buf[len] = 0;
close(fd);
return len < 0 ? -errno : len;
}
/* Returns written len on success, or -errno on failure. */
static ssize_t write_text(const char *path, char *buf, ssize_t len)
{
int fd;
ssize_t written;
fd = open(path, O_WRONLY | O_APPEND);
if (fd < 0)
return -errno;
written = write(fd, buf, len);
close(fd);
return written < 0 ? -errno : written;
}
long file_read_long(const char *path)
{
char buf[128];
if (read_text(path, buf, sizeof(buf)) <= 0)
return -1;
return atol(buf);
}
int file_write_long(const char *path, long val)
{
char buf[64];
int ret;
ret = sprintf(buf, "%ld", val);
if (ret < 0)
return ret;
if (write_text(path, buf, ret) <= 0)
return -1;
return 0;
}
struct scx_test_gated_worker scx_test_spawn_gated_worker(int cpu, bool set_sched_ext)
{
struct scx_test_gated_worker worker = { .pid = -1, .start_fd = -1 };
int ready[2], start[2];
pid_t parent = getpid();
char byte = 1;
if (pipe(ready))
return worker;
if (pipe(start)) {
close(ready[0]);
close(ready[1]);
return worker;
}
worker.pid = fork();
if (!worker.pid) {
struct sched_param param = {};
cpu_set_t mask;
close(ready[0]);
close(start[1]);
if (prctl(PR_SET_PDEATHSIG, SIGKILL) || getppid() != parent)
_exit(1);
CPU_ZERO(&mask);
CPU_SET(cpu, &mask);
if (sched_setaffinity(0, sizeof(mask), &mask))
_exit(1);
if (set_sched_ext && sched_setscheduler(0, SCHED_EXT, ¶m))
_exit(1);
if (write(ready[1], &byte, 1) != 1)
_exit(1);
close(ready[1]);
if (read(start[0], &byte, 1) != 1)
_exit(1);
close(start[0]);
for (;;)
asm volatile("" ::: "memory");
}
if (worker.pid < 0) {
close(ready[0]);
close(ready[1]);
close(start[0]);
close(start[1]);
return worker;
}
close(ready[1]);
close(start[0]);
if (read(ready[0], &byte, 1) != 1) {
close(ready[0]);
close(start[1]);
kill(worker.pid, SIGKILL);
waitpid(worker.pid, NULL, 0);
worker.pid = -1;
return worker;
}
close(ready[0]);
worker.start_fd = start[1];
return worker;
}
bool scx_test_start_gated_worker(struct scx_test_gated_worker *worker)
{
char byte = 1;
if (write(worker->start_fd, &byte, 1) != 1)
return false;
close(worker->start_fd);
worker->start_fd = -1;
return true;
}
void scx_test_stop_gated_worker(struct scx_test_gated_worker *worker)
{
if (worker->start_fd >= 0)
close(worker->start_fd);
if (worker->pid > 0) {
kill(worker->pid, SIGKILL);
waitpid(worker->pid, NULL, 0);
}
worker->pid = -1;
worker->start_fd = -1;
}
static int config_preempt_lazy_mode(void)
{
bool dynamic = false, lazy = false, immediate = false;
char buf[128];
gzFile file;
file = gzopen("/proc/config.gz", "r");
if (!file)
return -1;
while (gzgets(file, buf, sizeof(buf))) {
if (!strcmp(buf, "CONFIG_PREEMPT_DYNAMIC=y\n"))
dynamic = true;
else if (!strcmp(buf, "CONFIG_PREEMPT_LAZY=y\n"))
lazy = true;
else if (!strcmp(buf, "CONFIG_PREEMPT_NONE=y\n") ||
!strcmp(buf, "CONFIG_PREEMPT_VOLUNTARY=y\n") ||
!strcmp(buf, "CONFIG_PREEMPT=y\n") ||
!strcmp(buf, "CONFIG_PREEMPT_RT=y\n"))
immediate = true;
}
gzclose(file);
if (dynamic)
return -1;
if (lazy)
return 1;
if (immediate)
return 0;
return -1;
}
int scx_test_preempt_lazy_mode(void)
{
char buf[128];
if (read_text("/sys/kernel/debug/sched/preempt", buf, sizeof(buf)) > 0) {
if (strstr(buf, "(lazy)"))
return 1;
if (strstr(buf, "(none)") || strstr(buf, "(voluntary)") ||
strstr(buf, "(full)"))
return 0;
}
return config_preempt_lazy_mode();
}
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