1 files changed, 179 insertions, 0 deletions
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
new file mode 100644
index 0000000..c370311
--- /dev/null
+++ b/sys/kern/kern_sched.c
@@ -0,0 +1,179 @@
+/*
+ * 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/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.
+ *
+ * TODO
+ */
+void
+sched_switch(struct trapframe *tf)
+{
+    struct cpu_info *ci;
+    struct pcb *pcbp;
+    struct proc *next_td, *td;
+
+    ci = this_cpu();
+    td = ci->curtd;
+
+    /* Do we have threads to switch to? */
+    if ((next_td = sched_dequeue_td()) == NULL) {
+        sched_oneshot(false);
+        return;
+    }
+
+    /* 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);
+}