> Date: Sun, 13 Jul 2014 13:12:46 -0700
> From: Matthew Dempsky <matt...@dempsky.org>
>
> As the name suggests, remrunqueue(p) removes p from its run queue, and
> I believe that makes TAILQ_FOREACH() here unsafe. Instead of actually
> removing all threads from the processor, we'll only remove the first
> from each of its run queues.
>
> Diff below replaces TAILQ_FOREACH with the safe/idiomatic pattern for
> draining a queue.
>
> ok?
Ugh, yes.
> Index: kern_sched.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/kern_sched.c,v
> retrieving revision 1.32
> diff -u -p -r1.32 kern_sched.c
> --- kern_sched.c 4 May 2014 05:03:26 -0000 1.32
> +++ kern_sched.c 13 Jul 2014 20:18:38 -0000
> @@ -272,7 +272,7 @@ sched_chooseproc(void)
> if (spc->spc_schedflags & SPCF_SHOULDHALT) {
> if (spc->spc_whichqs) {
> for (queue = 0; queue < SCHED_NQS; queue++) {
> - TAILQ_FOREACH(p, &spc->spc_qs[queue], p_runq) {
> + while ((p = TAILQ_FIRST(&spc->spc_qs[queue]))) {
> remrunqueue(p);
> p->p_cpu = sched_choosecpu(p);
> setrunqueue(p);
>
>
