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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2023 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
*/
#define _GNU_SOURCE
#include <sched.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <tracefs.h>
#include <pthread.h>
#include <sys/wait.h>
#include <sys/prctl.h>
#include "utils.h"
#include "timerlat_u.h"
/*
* This is the user-space main for the tool timerlatu/ threads.
*
* It is as simple as this:
* - set affinity
* - set priority
* - open tracer fd
* - spin
* - close
*/
static int timerlat_u_main(int cpu, struct timerlat_u_params *params)
{
struct sched_param sp = { .sched_priority = 95 };
char buffer[1024];
int timerlat_fd;
cpu_set_t set;
int retval;
/*
* This all is only setting up the tool.
*/
CPU_ZERO(&set);
CPU_SET(cpu, &set);
retval = sched_setaffinity(gettid(), sizeof(set), &set);
if (retval == -1) {
err_msg("Error setting user thread affinity\n");
exit(1);
}
if (!params->sched_param) {
retval = sched_setscheduler(0, SCHED_FIFO, &sp);
if (retval < 0) {
err_msg("Error setting timerlat u default priority: %s\n", strerror(errno));
exit(1);
}
} else {
retval = __set_sched_attr(getpid(), params->sched_param);
if (retval) {
/* __set_sched_attr prints an error message, so */
exit(0);
}
}
if (params->cgroup_name) {
retval = set_pid_cgroup(gettid(), params->cgroup_name);
if (!retval) {
err_msg("Error setting timerlat u cgroup pid\n");
pthread_exit(&retval);
}
}
/*
* This is the tool's loop. If you want to use as base for your own tool...
* go ahead.
*/
snprintf(buffer, sizeof(buffer), "osnoise/per_cpu/cpu%d/timerlat_fd", cpu);
timerlat_fd = tracefs_instance_file_open(NULL, buffer, O_RDONLY);
if (timerlat_fd < 0) {
err_msg("Error opening %s:%s\n", buffer, strerror(errno));
exit(1);
}
debug_msg("User-space timerlat pid %d on cpu %d\n", gettid(), cpu);
/* add should continue with a signal handler */
while (true) {
retval = read(timerlat_fd, buffer, 1024);
if (retval < 0)
break;
}
close(timerlat_fd);
debug_msg("Leaving timerlat pid %d on cpu %d\n", gettid(), cpu);
exit(0);
}
/*
* timerlat_u_send_kill - send a kill signal for all processes
*
* Return the number of processes that received the kill.
*/
static int timerlat_u_send_kill(pid_t *procs, int nr_cpus)
{
int killed = 0;
int i, retval;
for (i = 0; i < nr_cpus; i++) {
if (!procs[i])
continue;
retval = kill(procs[i], SIGKILL);
if (!retval)
killed++;
else
err_msg("Error killing child process %d\n", procs[i]);
}
return killed;
}
/**
* timerlat_u_dispatcher - dispatch one timerlatu/ process per monitored CPU
*
* This is a thread main that will fork one new process for each monitored
* CPU. It will wait for:
*
* - rtla to tell to kill the child processes
* - some child process to die, and the cleanup all the processes
*
* whichever comes first.
*
*/
void *timerlat_u_dispatcher(void *data)
{
int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
struct timerlat_u_params *params = data;
char proc_name[128];
int procs_count = 0;
int retval = 1;
pid_t *procs;
int wstatus;
pid_t pid;
int i;
debug_msg("Dispatching timerlat u procs\n");
procs = calloc(nr_cpus, sizeof(pid_t));
if (!procs)
pthread_exit(&retval);
for (i = 0; i < nr_cpus; i++) {
if (params->set && !CPU_ISSET(i, params->set))
continue;
pid = fork();
/* child */
if (!pid) {
/*
* rename the process
*/
snprintf(proc_name, sizeof(proc_name), "timerlatu/%d", i);
pthread_setname_np(pthread_self(), proc_name);
prctl(PR_SET_NAME, (unsigned long)proc_name, 0, 0, 0);
timerlat_u_main(i, params);
/* timerlat_u_main should exit()! Anyways... */
pthread_exit(&retval);
}
/* parent */
if (pid == -1) {
timerlat_u_send_kill(procs, nr_cpus);
debug_msg("Failed to create child processes");
pthread_exit(&retval);
}
procs_count++;
procs[i] = pid;
}
while (params->should_run) {
/* check if processes died */
pid = waitpid(-1, &wstatus, WNOHANG);
if (pid != 0) {
for (i = 0; i < nr_cpus; i++) {
if (procs[i] == pid) {
procs[i] = 0;
procs_count--;
}
}
break;
}
sleep(1);
}
timerlat_u_send_kill(procs, nr_cpus);
while (procs_count) {
pid = waitpid(-1, &wstatus, 0);
if (pid == -1) {
err_msg("Failed to monitor child processes");
pthread_exit(&retval);
}
for (i = 0; i < nr_cpus; i++) {
if (procs[i] == pid) {
procs[i] = 0;
procs_count--;
}
}
}
params->stopped_running = 1;
free(procs);
retval = 0;
pthread_exit(&retval);
}
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