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-rw-r--r--sys/kern/kern_sched.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index 77aab54..7b3776d 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -360,18 +360,23 @@ sched_context_switch(struct trapframe *tf)
return;
}
+ /*
+ * If we have a thread currently running and we are switching
+ * to another, we shall save our current register state
+ * by copying the trapframe.
+ */
if (state->td != NULL) {
- /* Save our trapframe */
td = state->td;
memcpy(td->tf, tf, sizeof(struct trapframe));
}
- /* Copy to stack */
+ /* Copy over the next thread's register state to us */
memcpy(tf, next_td->tf, sizeof(struct trapframe));
td = state->td;
state->td = next_td;
+ /* Re-enqueue the previous thread if it exists */
if (td != NULL) {
sched_enqueue_td(td);
}