Re: [tip:sched/core] sched: Check for an idle shared cache in select_task_rq_fair()

Mike Galbraith
2009-11-05T09:57:47Z

On Thu, 2009-11-05 at 10:30 +0100, Ingo Molnar wrote:
> * tip-bot for Mike Galbraith <efault@gmx.de> wrote:
>
> > Commit-ID: a1f84a3ab8e002159498814eaa7e48c33752b04b
> > Gitweb: http://git.kernel.org/tip/a1f84a3ab8e002159498814eaa7e48c33752b04b
> > Author: Mike Galbraith <efault@gmx.de>
> > AuthorDate: Tue, 27 Oct 2009 15:35:38 +0100
> > Committer: Ingo Molnar <mingo@elte.hu>
> > CommitDate: Wed, 4 Nov 2009 18:46:22 +0100
> >
> > sched: Check for an idle shared cache in select_task_rq_fair()
>
> -tip testing found that this causes problems:
>
> [ 26.804000] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/10
> [ 26.808000] caller is vmstat_update+0x26/0x70
> [ 26.812000] Pid: 10, comm: events/1 Not tainted 2.6.32-rc5 #6887
> [ 26.816000] Call Trace:
> [ 26.820000] [<c1924a24>] ? printk+0x28/0x3c
> [ 26.824000] [<c13258a0>] debug_smp_processor_id+0xf0/0x110
> [ 26.824000] mount used greatest stack depth: 1464 bytes left
> [ 26.828000] [<c111d086>] vmstat_update+0x26/0x70
> [ 26.832000] [<c1086418>] worker_thread+0x188/0x310
> [ 26.836000] [<c10863b7>] ? worker_thread+0x127/0x310
> [ 26.840000] [<c108d310>] ? autoremove_wake_function+0x0/0x60
> [ 26.844000] [<c1086290>] ? worker_thread+0x0/0x310
> [ 26.848000] [<c108cf0c>] kthread+0x7c/0x90
> [ 26.852000] [<c108ce90>] ? kthread+0x0/0x90
> [ 26.856000] [<c100c0a7>] kernel_thread_helper+0x7/0x10
> [ 26.860000] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/10
> [ 26.864000] caller is vmstat_update+0x3c/0x70
>
> oh ... doesnt it break cpus_allowed?

Erk, indeed. You didn't apply the follow-up fix, and I forgot as well.

sched: select_task_rq_fair():: add missing cpu allowed check in commit a1f84a3.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 32f06ed..5488a5d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1415,6 +1415,8 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag

if (candidate == -1 || candidate == cpu) {
for_each_cpu(i, sched_domain_span(tmp)) {
+ if (!cpumask_test_cpu(i, &p->cpus_allowed))
+ continue;
if (!cpu_rq(i)->cfs.nr_running) {
candidate = i;
break;