linux-kernel - Re: [PATCH] riscv: Fix local irq restore when flags indicates irq disabled

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Date:   Tue, 08 Aug 2023 23:05:11 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     luxu.kernel@...edance.com
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        luxu.kernel@...edance.com
Subject:     Re: [PATCH] riscv: Fix local irq restore when flags indicates irq disabled

On Tue, 25 Jul 2023 00:05:49 PDT (-0700), luxu.kernel@...edance.com wrote:
> When arch_local_irq_restore() is called with flags indicating irqs
> disabled, we need to clear SR_IE bit in CSR_STATUS, whereas current
> implementation based on csr_set() function only sets SR_IE bit of
> CSR_STATUS when SR_IE bit of flags is high and does nothing when
> SR_IE bit of flags is low.
>
> This commit supplies csr clear operation when calling irq restore
> function with flags indicating irq disabled.
>
> Fixes: 6d60b6ee0c97 ("RISC-V: Device, timer, IRQs, and the SBI")
> Signed-off-by: Xu Lu <luxu.kernel@...edance.com>
> ---
>  arch/riscv/include/asm/irqflags.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/irqflags.h b/arch/riscv/include/asm/irqflags.h
> index 08d4d6a5b7e9..7c31fc3c3559 100644
> --- a/arch/riscv/include/asm/irqflags.h
> +++ b/arch/riscv/include/asm/irqflags.h
> @@ -49,7 +49,10 @@ static inline int arch_irqs_disabled(void)
>  /* set interrupt enabled status */
>  static inline void arch_local_irq_restore(unsigned long flags)
>  {
> -	csr_set(CSR_STATUS, flags & SR_IE);
> +	if (flags & SR_IE)
> +		csr_set(CSR_STATUS, SR_IE);
> +	else
> +		csr_clear(CSR_STATUS, SR_IE);

Unless I'm missing something, the original version is correct: 
local_irq_restore() must be paired with a local_irq_save(), so we can 
only get here with interrupts disabled.

>  }
>
>  #endif /* _ASM_RISCV_IRQFLAGS_H */