[src/trunk]: src/sys/kern sched_tick: examine the correct LWP, and lock it.

[ad <ad%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/c4d57ff63be1
branches:  trunk
changeset: 461320:c4d57ff63be1
user:      ad <ad%NetBSD.org@localhost>
date:      Fri Nov 22 20:07:53 2019 +0000

description:
sched_tick: examine the correct LWP, and lock it.

diffstat:

 sys/kern/sched_m2.c |  17 ++++++++++-------
 1 files changed, 10 insertions(+), 7 deletions(-)

diffs (63 lines):

diff -r 04cb4785678c -r c4d57ff63be1 sys/kern/sched_m2.c
--- a/sys/kern/sched_m2.c       Fri Nov 22 20:04:03 2019 +0000
+++ b/sys/kern/sched_m2.c       Fri Nov 22 20:07:53 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sched_m2.c,v 1.33 2018/09/03 16:29:35 riastradh Exp $  */
+/*     $NetBSD: sched_m2.c,v 1.34 2019/11/22 20:07:53 ad Exp $ */
 
 /*
  * Copyright (c) 2007, 2008 Mindaugas Rasiukevicius <rmind at NetBSD org>
@@ -33,7 +33,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sched_m2.c,v 1.33 2018/09/03 16:29:35 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sched_m2.c,v 1.34 2019/11/22 20:07:53 ad Exp $");
 
 #include <sys/param.h>
 
@@ -282,19 +282,20 @@
  */
 
 /*
- * Called once per time-quantum.  This routine is CPU-local and runs at
- * IPL_SCHED, thus the locking is not needed.
+ * Called once per time-quantum, with the running LWP lock held (spc_lwplock).
  */
 void
 sched_tick(struct cpu_info *ci)
 {
        struct schedstate_percpu *spc = &ci->ci_schedstate;
-       struct lwp *l = curlwp;
+       struct lwp *l = ci->ci_data.cpu_onproc;
        struct proc *p;
 
        if (__predict_false(CURCPU_IDLE_P()))
                return;
 
+       lwp_lock(l);
+       KASSERT(l->l_mutex != spc->spc_mutex);
        switch (l->l_class) {
        case SCHED_FIFO:
                /*
@@ -303,6 +304,7 @@
                 */
                KASSERT(l->l_priority > PRI_HIGHEST_TS);
                spc->spc_ticks = l->l_sched.timeslice;
+               lwp_unlock(l);
                return;
        case SCHED_OTHER:
                /*
@@ -328,9 +330,10 @@
         */
        if (lwp_eprio(l) <= spc->spc_maxpriority || l->l_target_cpu) {
                spc->spc_flags |= SPCF_SHOULDYIELD;
-               cpu_need_resched(ci, 0);
+               cpu_need_resched(ci, l, RESCHED_UPREEMPT);
        } else
-               spc->spc_ticks = l->l_sched.timeslice;
+               spc->spc_ticks = l->l_sched.timeslice; 
+       lwp_unlock(l);
 }
 
 /*