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

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Date:   Tue, 11 Dec 2018 14:41:57 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Bartosz Golaszewski <brgl@...ev.pl>,
        Thomas Gleixner <tglx@...utronix.de>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] irq/irq_sim: store multiple interrupt offsets in a bitmap

On 11/12/2018 14:02, Bartosz Golaszewski wrote:
> 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?

Bizarrely, I can't find any trace of this patch in my Inbox. I've now
cherry-picked from https://lore.kernel.org/patchwork/patch/1009297/ .

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...