linux-kernel - RE: [PATCH] crypto: amlogic - Save a few bytes of memory

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Date:   Wed, 23 Nov 2022 00:03:28 +0000
From:   "Elliott, Robert (Servers)" <elliott@....com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
CC:     Corentin Labbe <clabbe@...libre.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-amlogic@...ts.infradead.org" 
        <linux-amlogic@...ts.infradead.org>
Subject: RE: [PATCH] crypto: amlogic - Save a few bytes of memory



> -----Original Message-----
> From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> Sent: Tuesday, November 22, 2022 4:37 PM
> Subject: Re: [PATCH] crypto: amlogic - Save a few bytes of memory


...
> Unrelated, but I think that meson_irq_handler() needs a small ajustement
> to avoid printing a spurious message if readl() returns 0.
> 
> Maybe something like that?:
> 
> @@ -33,9 +33,10 @@ static irqreturn_t meson_irq_handler(int irq, void
> *data)
>   				writel_relaxed(0xF, mc->base + ((0x4 + flow) << 2));
>   				mc->chanlist[flow].status = 1;
>   				complete(&mc->chanlist[flow].complete);
> -				return IRQ_HANDLED;
> +			} else {
> +				dev_err(mc->dev, "%s %d Got irq for flow %d but ctrl is empty\n", __func__, irq, flow);
>   			}
> -			dev_err(mc->dev, "%s %d Got irq for flow %d but ctrl is empty\n", __func__, irq, flow);
> +			return IRQ_HANDLED;
>   		}
>   	}

You might want to reconsider allowing this irq handler to do any prints.
80 characters take 5 ms to print on a 115 kbps serial port, which can
lead to RCU stalls, soft lockups, etc.

If kept, dev_err_ratelimited would be a little safer.

In some systems "spurious interrupts" are routine and are not really a
problem unless you overreact to them.