linux-kernel - Re: [PATCH v2 3/4] irq_work: Handle some irq_work in a per-CPU thread on PREEMPT

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Date:   Wed, 6 Oct 2021 13:35:29 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 3/4] irq_work: Handle some irq_work in a per-CPU
 thread on PREEMPT_RT

On 2021-10-06 13:18:51 [+0200], To linux-kernel@...r.kernel.org wrote:
> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> index e789beda8297d..daa5d12522faa 100644
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -18,11 +18,34 @@
>  #include <linux/cpu.h>
>  #include <linux/notifier.h>
>  #include <linux/smp.h>
> +#include <linux/smpboot.h>
>  #include <asm/processor.h>
>  #include <linux/kasan.h>
>  
>  static DEFINE_PER_CPU(struct llist_head, raised_list);
>  static DEFINE_PER_CPU(struct llist_head, lazy_list);
> +static DEFINE_PER_CPU(struct task_struct *, irq_workd);
> +
> +static void wake_irq_workd(void)
> +{
> +	struct task_struct *tsk = __this_cpu_read(irq_workd);
> +
> +	if (!llist_empty(this_cpu_ptr(&lazy_list)) && tsk)
> +		wake_up_process(tsk);
> +}

#ifdef CONFIG_SMP

> +static void irq_work_wake(struct irq_work *entry)
> +{
> +	wake_irq_workd();
> +}
> +
> +static DEFINE_PER_CPU(struct irq_work, irq_work_pending) =
> +	IRQ_WORK_INIT_HARD(irq_work_wake);

#endif

> +static int irq_workd_should_run(unsigned int cpu)
> +{
> +	return !llist_empty(this_cpu_ptr(&lazy_list));
> +}
>  
>  /*
>   * Claim the entry so that no one else will poke at it.

Sebastian