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/*
* Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Hyra nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/types.h>
#include <sys/sched.h>
#include <sys/schedvar.h>
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/syslog.h>
#include <machine/frame.h>
#include <machine/cpu.h>
#include <vm/pmap.h>
#include <dev/timer.h>
#include <assert.h>
#include <string.h>
#define pr_trace(fmt, ...) kprintf("ksched: " fmt, ##__VA_ARGS__)
void sched_switch(struct trapframe *tf);
static sched_policy_t policy = SCHED_POLICY_RR;
/*
* Thread ready queues - all threads ready to be
* scheduled should be added to the toplevel queue.
*/
static struct sched_queue qlist[SCHED_NQUEUE];
/*
* Thread queue lock - all operations to `qlist'
* must be done with this lock acquired.
*/
__cacheline_aligned static struct spinlock tdq_lock = {0};
/*
* Perform timer oneshot
*/
static inline void
sched_oneshot(bool now)
{
struct timer timer;
size_t usec = now ? SHORT_TIMESLICE_USEC : DEFAULT_TIMESLICE_USEC;
tmrr_status_t tmr_status;
tmr_status = req_timer(TIMER_SCHED, &timer);
__assert(tmr_status == TMRR_SUCCESS);
timer.oneshot_us(usec);
}
static struct proc *
sched_dequeue_td(void)
{
struct sched_queue *queue;
struct proc *td = NULL;
spinlock_acquire(&tdq_lock);
for (size_t i = 0; i < SCHED_NQUEUE; ++i) {
queue = &qlist[i];
if (!TAILQ_EMPTY(&queue->q)) {
td = TAILQ_FIRST(&queue->q);
TAILQ_REMOVE(&queue->q, td, link);
break;
}
}
spinlock_release(&tdq_lock);
return td;
}
/*
* Add a thread to the scheduler.
*/
void
sched_enqueue_td(struct proc *td)
{
struct sched_queue *queue;
spinlock_acquire(&tdq_lock);
queue = &qlist[td->priority];
TAILQ_INSERT_TAIL(&queue->q, td, link);
spinlock_release(&tdq_lock);
}
/*
* Return the currently running thread.
*/
struct proc *
this_td(void)
{
struct cpu_info *ci;
ci = this_cpu();
return ci->curtd;
}
/*
* Perform a context switch.
*/
void
sched_switch(struct trapframe *tf)
{
struct cpu_info *ci;
struct pcb *pcbp;
struct proc *next_td, *td;
bool use_current = true;
bool inexec;
ci = this_cpu();
td = ci->curtd;
/*
* Get the next thread and use it only if it isn't
* in the middle of an exit, exec, or whatever.
*/
do {
if ((next_td = sched_dequeue_td()) == NULL) {
sched_oneshot(false);
return;
}
/*
* Don't use this thread if we are currently
* exiting.
*/
if (ISSET(next_td->flags, PROC_EXITING)) {
use_current = false;
}
} while (!use_current);
/* Re-enqueue the old thread */
if (td != NULL) {
memcpy(&td->tf, tf, sizeof(td->tf));
sched_enqueue_td(td);
}
memcpy(tf, &next_td->tf, sizeof(*tf));
ci->curtd = next_td;
pcbp = &next_td->pcb;
pmap_switch_vas(pcbp->addrsp);
sched_oneshot(false);
}
/*
* Main scheduler loop
*/
void
sched_enter(void)
{
sched_oneshot(false);
for (;;);
}
void
sched_init(void)
{
/* Setup the queues */
for (int i = 0; i < SCHED_NQUEUE; ++i) {
TAILQ_INIT(&qlist[i].q);
}
pr_trace("Prepared %d queues (policy=0x%x)\n",
SCHED_NQUEUE, policy);
}
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