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Date: Thu, 7 Jul 2022 14:49:07 +0200
From: Arnd Bergmann <arnd@...db.de>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK
On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@...edance.com> wrote:
>
> Since softirqs are handled on the per-CPU IRQ stack,
> let's support HAVE_IRQ_EXIT_ON_IRQ_STACK which causes
> the core code to invoke __do_softirq() directly without
> going through do_softirq_own_stack().
>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
I think the idea is right, but the extra function pointer adds more complexity
than necessary:
> static __always_inline void __el1_irq(struct pt_regs *regs,
> void (*handler)(struct pt_regs *))
> {
> enter_from_kernel_mode(regs);
>
> - irq_enter_rcu();
> - do_interrupt_handler(regs, handler);
> - irq_exit_rcu();
> + do_interrupt_handler(regs, handler, irq_handler);
>
> arm64_preempt_schedule_irq();
>
> @@ -699,9 +711,7 @@ static void noinstr el0_interrupt(struct pt_regs *regs,
> if (regs->pc & BIT(55))
> arm64_apply_bp_hardening();
>
> - irq_enter_rcu();
> - do_interrupt_handler(regs, handler);
> - irq_exit_rcu();
> + do_interrupt_handler(regs, handler, irq_handler);
>
> exit_to_user_mode(regs);
> }
Would it be possible to instead pull out the call_on_irq_stack() so these
two functions are instead called on the IRQ stack already?
Arnd
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