linux-kernel - Re: [PATCH] irq/irq_sim: store multiple interrupt offsets in a bitmap

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Date:   Tue, 11 Dec 2018 15:02:48 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] irq/irq_sim: store multiple interrupt offsets in a bitmap

pt., 9 lis 2018 o 18:21 Bartosz Golaszewski <brgl@...ev.pl> napisał(a):
>
> Two threads can try to fire the irq_sim with different offsets and will
> end up fighting for the irq_work asignment. Thomas Gleixner suggested a
> solution based on a bitfield where we set a bit for every offset
> associated with an interrupt that should be fired and then iterate over
> all set bits in the interrupt handler.
>
> This is a slightly modified solution using a bitmap so that we don't
> impose a limit on the number of interrupts one can allocate with
> irq_sim.
>
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Bartosz Golaszewski <brgl@...ev.pl>
> ---
>  include/linux/irq_sim.h |  2 +-
>  kernel/irq/irq_sim.c    | 23 +++++++++++++++++++++--
>  2 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/irq_sim.h b/include/linux/irq_sim.h
> index 630a57e55db6..4500d453a63e 100644
> --- a/include/linux/irq_sim.h
> +++ b/include/linux/irq_sim.h
> @@ -16,7 +16,7 @@
>
>  struct irq_sim_work_ctx {
>         struct irq_work         work;
> -       int                     irq;
> +       unsigned long           *pending;
>  };
>
>  struct irq_sim_irq_ctx {
> diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
> index dd20d0d528d4..98a20e1594ce 100644
> --- a/kernel/irq/irq_sim.c
> +++ b/kernel/irq/irq_sim.c
> @@ -34,9 +34,20 @@ static struct irq_chip irq_sim_irqchip = {
>  static void irq_sim_handle_irq(struct irq_work *work)
>  {
>         struct irq_sim_work_ctx *work_ctx;
> +       unsigned int offset = 0;
> +       struct irq_sim *sim;
> +       int irqnum;
>
>         work_ctx = container_of(work, struct irq_sim_work_ctx, work);
> -       handle_simple_irq(irq_to_desc(work_ctx->irq));
> +       sim = container_of(work_ctx, struct irq_sim, work_ctx);
> +
> +       while (!bitmap_empty(work_ctx->pending, sim->irq_count)) {
> +               offset = find_next_bit(work_ctx->pending,
> +                                      sim->irq_count, offset);
> +               clear_bit(offset, work_ctx->pending);
> +               irqnum = irq_sim_irqnum(sim, offset);
> +               handle_simple_irq(irq_to_desc(irqnum));
> +       }
>  }
>
>  /**
> @@ -63,6 +74,13 @@ int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
>                 return sim->irq_base;
>         }
>
> +       sim->work_ctx.pending = bitmap_zalloc(num_irqs, GFP_KERNEL);
> +       if (!sim->work_ctx.pending) {
> +               kfree(sim->irqs);
> +               irq_free_descs(sim->irq_base, num_irqs);
> +               return -ENOMEM;
> +       }
> +
>         for (i = 0; i < num_irqs; i++) {
>                 sim->irqs[i].irqnum = sim->irq_base + i;
>                 sim->irqs[i].enabled = false;
> @@ -89,6 +107,7 @@ EXPORT_SYMBOL_GPL(irq_sim_init);
>  void irq_sim_fini(struct irq_sim *sim)
>  {
>         irq_work_sync(&sim->work_ctx.work);
> +       bitmap_free(sim->work_ctx.pending);
>         irq_free_descs(sim->irq_base, sim->irq_count);
>         kfree(sim->irqs);
>  }
> @@ -143,7 +162,7 @@ EXPORT_SYMBOL_GPL(devm_irq_sim_init);
>  void irq_sim_fire(struct irq_sim *sim, unsigned int offset)
>  {
>         if (sim->irqs[offset].enabled) {
> -               sim->work_ctx.irq = irq_sim_irqnum(sim, offset);
> +               set_bit(offset, sim->work_ctx.pending);
>                 irq_work_queue(&sim->work_ctx.work);
>         }
>  }
> --
> 2.19.1
>

Ping and Cc'ing Marc Zyngier. Any chance of getting this in for 4.21?

Bart