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SubjectRe: single_task_running() vs. preemption warnings (was Re: [PATCH] kvm: fix preemption warnings in kvm_vcpu_block)
On Thu, Sep 17, 2015 at 01:32:55PM -0700, Tim Chen wrote:
> I have no objection to change single_task_running to use
> raw_smp_processor_id. The worker in mcryptd is bound to
> the cpu so it has no migration/preemption issue. So it shouldn't care
> which smp_processor_id version is being used. Yes, please add a comment
> to alert the user of this caveat should you change single_task_running.


We actually have raw_rq() for that, and the whole if thing looks rather
superfluous. So something like the below, except with a suitable comment
on and tested etc.. ;-)

---
kernel/sched/core.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6ab415aa15c4..f39c0498e284 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2666,10 +2666,7 @@ unsigned long nr_running(void)
*/
bool single_task_running(void)
{
- if (cpu_rq(smp_processor_id())->nr_running == 1)
- return true;
- else
- return false;
+ return raw_rq()->nr_running == 1;
}
EXPORT_SYMBOL(single_task_running);


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