clockintr_dispatch: add intermediate pointer for clockintr_queue.cq_shadow

Adding an intermediate pointer lets me shortens "cq->cq_shadow" to
just "shadow".  I think it makes the dispatch loop logic a little
easier to read.

While here, add a clarifying comment.

diff --git a/sys/kern/kern_clockintr.c b/sys/kern/kern_clockintr.c
index d941814..6edc5d0 100644 (file)
--- a/sys/kern/kern_clockintr.c
+++ b/sys/kern/kern_clockintr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kern_clockintr.c,v 1.45 2023/09/09 17:07:59 cheloha Exp $ */
+/* $OpenBSD: kern_clockintr.c,v 1.46 2023/09/10 01:41:16 cheloha Exp $ */
 /*
  * Copyright (c) 2003 Dale Rahn <drahn@openbsd.org>
  * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
@@ -219,7 +219,7 @@ clockintr_dispatch(void *frame)
 {
        uint64_t lateness, run = 0, start;
        struct cpu_info *ci = curcpu();
-       struct clockintr *cl;
+       struct clockintr *cl, *shadow;
        struct clockintr_queue *cq = &ci->ci_queue;
        uint32_t ogen;
 
@@ -257,24 +257,29 @@ clockintr_dispatch(void *frame)
                        if (cq->cq_uptime < cl->cl_expiration)
                                break;
                }
+
+               /*
+                * This clockintr has expired.  Initialize a shadow copy
+                * and execute it.
+                */
                clockqueue_pend_delete(cq, cl);
-               cq->cq_shadow.cl_expiration = cl->cl_expiration;
-               cq->cq_shadow.cl_func = cl->cl_func;
+               shadow = &cq->cq_shadow;
+               shadow->cl_expiration = cl->cl_expiration;
+               shadow->cl_func = cl->cl_func;
                cq->cq_running = cl;
                mtx_leave(&cq->cq_mtx);
 
-               cq->cq_shadow.cl_func(&cq->cq_shadow, frame);
+               shadow->cl_func(shadow, frame);
 
                mtx_enter(&cq->cq_mtx);
                cq->cq_running = NULL;
                if (ISSET(cl->cl_flags, CLST_IGNORE_SHADOW)) {
                        CLR(cl->cl_flags, CLST_IGNORE_SHADOW);
-                       CLR(cq->cq_shadow.cl_flags, CLST_SHADOW_PENDING);
+                       CLR(shadow->cl_flags, CLST_SHADOW_PENDING);
                }
-               if (ISSET(cq->cq_shadow.cl_flags, CLST_SHADOW_PENDING)) {
-                       CLR(cq->cq_shadow.cl_flags, CLST_SHADOW_PENDING);
-                       clockqueue_pend_insert(cq, cl,
-                           cq->cq_shadow.cl_expiration);
+               if (ISSET(shadow->cl_flags, CLST_SHADOW_PENDING)) {
+                       CLR(shadow->cl_flags, CLST_SHADOW_PENDING);
+                       clockqueue_pend_insert(cq, cl, shadow->cl_expiration);
                }
                run++;
        }