sched_dl.c

/*
 Copyright (c) 2017 Dan Hallgren  <dan.hallgren@gmail.com>

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.

 */

//#define _GNU_SOURCE
#include <unistd.h>
#include <linux/unistd.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <sys/syscall.h>
#include <sched.h>

#include "sched_dl.h"

#define gettid() syscall(__NR_gettid)

#define SCHED_DEADLINE	6

/* XXX use the proper syscall numbers */
#ifdef __x86_64__
#define __NR_sched_setattr		314
#define __NR_sched_getattr		315
#endif

#ifdef __i386__
#define __NR_sched_setattr		351
#define __NR_sched_getattr		352
#endif

#ifdef __arm__
#define __NR_sched_setattr		380
#define __NR_sched_getattr		381
#endif

struct sched_attr
{
    __u32 size;

    __u32 sched_policy;
    __u64 sched_flags;

    /* SCHED_NORMAL, SCHED_BATCH */
    __s32 sched_nice;

    /* SCHED_FIFO, SCHED_RR */
    __u32 sched_priority;

    /* SCHED_DEADLINE (nsec) */
    __u64 sched_runtime;
    __u64 sched_deadline;
    __u64 sched_period;
};

static int sched_setattr (pid_t pid, const struct sched_attr *attr, unsigned int flags)
{
    return syscall (__NR_sched_setattr, pid, attr, flags);
}

static int sched_getattr (pid_t pid, struct sched_attr *attr, unsigned int size, unsigned int flags)
{
    return syscall (__NR_sched_getattr, pid, attr, size, flags);
}

int set_current_tid_to_deadline (__u64 runtime, __u64 deadline, __u64 period, unsigned int flags)
{
    struct sched_attr attr;
    int ret;

    ret = sched_getattr (0, &attr, sizeof(struct sched_attr), 0);
    if (ret < 0) {
        return ret;
    }

    attr.sched_policy = SCHED_DEADLINE;
    attr.sched_runtime = runtime;
    attr.sched_deadline = deadline;
    attr.sched_period = period;
    attr.sched_flags = flags;

    ret = sched_setattr (0, &attr, 0);
    if (ret < 0) {
        return ret;
    }

    return 0;
}

void sched_dl_yield (void)
{
    (void) sched_yield ();
}