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From: Thomas Gleixner <tglx@linutronix.de>
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To: Yury Norov <yury.norov@gmail.com>
Cc: linux-kernel@vger.kernel.org, Bartosz Golaszewski
 <bartosz.golaszewski@linaro.org>
Subject: Re: [PATCH] irq: simplify irq_im_handle_irq()
In-Reply-To: <aH5OUChoFx55WnVG@yury>
References: <20250719211818.402115-1-yury.norov@gmail.com>
 <87zfcxtz6t.ffs@tglx> <aH5OUChoFx55WnVG@yury>
Date: Mon, 21 Jul 2025 17:44:16 +0200
Message-ID: <87o6tdtupb.ffs@tglx>
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On Mon, Jul 21 2025 at 10:27, Yury Norov wrote:
> On Mon, Jul 21, 2025 at 04:07:22PM +0200, Thomas Gleixner wrote:
> find_next_bit() and for_each_bit() cannot be used in concurrent
> environment, and having atomic clear_bit() is meaningless here.
> Two concurrent processes, if running in parallel, may pick the
> same offset, ending up executing the handle_simple_irq() twice.

The irq work cannot be run in parallel on multiple CPUs. It's guaranteed
that only one irq work handler runs at a time. So irq_sim_handle_irq()
is fully serialized by the irq work magic.

But the bitmap can be modified concurrently, which is not a problem.

Thanks,

        tglx