From f6900b5c3b4832f48359fd761b80f8693a6735e8 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 16 Jul 2025 20:44:54 -0400
Subject: kernel: Sort out switch MI/MD switch logic

Certain operations dealing with context switches are better off being
implemented as machine dependent routines which allows us to be flexible
with what we can do, as well as the extra benefit of requiring less
workarounds to keep things MI.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/kern/kern_sched.c | 70 ++++++++-------------------------------------------
 1 file changed, 11 insertions(+), 59 deletions(-)

(limited to 'sys/kern')

diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index 02d19df..e259a2c 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -45,7 +45,7 @@
 
 #define pr_trace(fmt, ...) kprintf("ksched: " fmt, ##__VA_ARGS__)
 
-void sched_switch(struct trapframe *tf);
+void md_sched_switch(struct trapframe *tf);
 void sched_accnt_init(void);
 
 static sched_policy_t policy = SCHED_POLICY_MLFQ;
@@ -65,7 +65,7 @@ __cacheline_aligned static struct spinlock tdq_lock = {0};
 /*
  * Perform timer oneshot
  */
-static inline void
+void
 sched_oneshot(bool now)
 {
     struct timer timer;
@@ -78,25 +78,7 @@ sched_oneshot(bool now)
     timer.oneshot_us(usec);
 }
 
-/*
- * Save thread state and enqueue it back into one
- * of the ready queues.
- */
-static void
-sched_save_td(struct proc *td, struct trapframe *tf)
-{
-    /*
-     * Save trapframe to process structure only
-     * if PROC_EXEC is not set.
-     */
-    if (!ISSET(td->flags, PROC_EXEC)) {
-        memcpy(&td->tf, tf, sizeof(td->tf));
-    }
-
-    sched_enqueue_td(td);
-}
-
-static struct proc *
+struct proc *
 sched_dequeue_td(void)
 {
     struct sched_queue *queue;
@@ -198,52 +180,22 @@ td_pri_update(struct proc *td)
     }
 }
 
-void
-sched_switch_to(struct trapframe *tf, struct proc *td)
-{
-    struct cpu_info *ci;
-    struct pcb *pcbp;
-
-    ci = this_cpu();
-
-    if (tf != NULL) {
-        memcpy(tf, &td->tf, sizeof(*tf));
-    }
-
-    ci->curtd = td;
-    pcbp = &td->pcb;
-    pmap_switch_vas(pcbp->addrsp);
-}
-
 /*
- * Perform a context switch.
+ * MI work to be done during a context
+ * switch. Called by md_sched_switch()
  */
 void
-sched_switch(struct trapframe *tf)
+mi_sched_switch(struct proc *from)
 {
-    struct proc *next_td, *td;
-    struct cpu_info *ci;
-
-    ci = this_cpu();
-    td = ci->curtd;
-    cons_detach();
-
-    if (td != NULL) {
-        if (td->pid == 0)
+    if (from != NULL) {
+        if (from->pid == 0)
             return;
 
-        dispatch_signals(td);
-        td_pri_update(td);
-        sched_save_td(td, tf);
+        dispatch_signals(from);
+        td_pri_update(from);
     }
 
-    if ((next_td = sched_dequeue_td()) == NULL) {
-        sched_oneshot(false);
-        return;
-    }
-
-    sched_switch_to(tf, next_td);
-    sched_oneshot(false);
+    cons_detach();
 }
 
 /*
-- 
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