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SubjectRe: [RFC PATCH] sched: Introduce per-mm/cpu concurrency id state
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On 2023-03-31 04:38, Aaron Lu wrote:
> On Thu, Mar 30, 2023 at 07:09:11PM -0400, Mathieu Desnoyers wrote:
>
>> void sched_mm_cid_exit_signals(struct task_struct *t)
>> {
>> struct mm_struct *mm = t->mm;
>> - unsigned long flags;
>> + struct rq *rq = this_rq();
>
> Got many below messages due to the above line:
>
> [ 19.294089] BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u449:0/1621
>
>> + struct rq_flags rf;
>>
>> if (!mm)
>> return;
>> - local_irq_save(flags);
>> + rq_lock_irqsave(rq, &rf);
>> mm_cid_put(mm, t->mm_cid);
>> t->mm_cid = -1;
>> t->mm_cid_active = 0;
>> - local_irq_restore(flags);
>> + rq_unlock_irqrestore(rq, &rf);
>> }
>>
>> void sched_mm_cid_before_execve(struct task_struct *t)
>> {
>> struct mm_struct *mm = t->mm;
>> - unsigned long flags;
>> + struct rq *rq = this_rq();
>
> Also here;
>
>> + struct rq_flags rf;
>>
>> if (!mm)
>> return;
>> - local_irq_save(flags);
>> + rq_lock_irqsave(rq, &rf);
>> mm_cid_put(mm, t->mm_cid);
>> t->mm_cid = -1;
>> t->mm_cid_active = 0;
>> - local_irq_restore(flags);
>> + rq_unlock_irqrestore(rq, &rf);
>> }
>>
>> void sched_mm_cid_after_execve(struct task_struct *t)
>> {
>> struct mm_struct *mm = t->mm;
>> - unsigned long flags;
>> + struct rq *rq = this_rq();
>
> And here.
>
>> + struct rq_flags rf;
>>
>> if (!mm)
>> return;
>> - local_irq_save(flags);
>> + rq_lock_irqsave(rq, &rf);
>> t->mm_cid = mm_cid_get(mm);
>> t->mm_cid_active = 1;
>> - local_irq_restore(flags);
>> + rq_unlock_irqrestore(rq, &rf);
>> rseq_set_notify_resume(t);
>> }
>
> I used below diff to get rid of these messages without understanding the
> purpose of these functions:

I'll fold this fix into the next round, thanks!

Mathieu

>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index f07b87d155bd..7194c29f3c91 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -11444,45 +11444,57 @@ void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t, int src_c
> void sched_mm_cid_exit_signals(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - struct rq *rq = this_rq();
> struct rq_flags rf;
> + struct rq *rq;
>
> if (!mm)
> return;
> +
> + preempt_disable();
> + rq = this_rq();
> rq_lock_irqsave(rq, &rf);
> mm_cid_put(mm, t->mm_cid);
> t->mm_cid = -1;
> t->mm_cid_active = 0;
> rq_unlock_irqrestore(rq, &rf);
> + preempt_enable();
> }
>
> void sched_mm_cid_before_execve(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - struct rq *rq = this_rq();
> struct rq_flags rf;
> + struct rq *rq;
>
> if (!mm)
> return;
> +
> + preempt_disable();
> + rq = this_rq();
> rq_lock_irqsave(rq, &rf);
> mm_cid_put(mm, t->mm_cid);
> t->mm_cid = -1;
> t->mm_cid_active = 0;
> rq_unlock_irqrestore(rq, &rf);
> + preempt_enable();
> }
>
> void sched_mm_cid_after_execve(struct task_struct *t)
> {
> struct mm_struct *mm = t->mm;
> - struct rq *rq = this_rq();
> struct rq_flags rf;
> + struct rq *rq;
>
> if (!mm)
> return;
> +
> + preempt_disable();
> + rq = this_rq();
> rq_lock_irqsave(rq, &rf);
> t->mm_cid = mm_cid_get(mm);
> t->mm_cid_active = 1;
> rq_unlock_irqrestore(rq, &rf);
> + preempt_enable();
> rseq_set_notify_resume(t);
> }
>

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com

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