From: Heiner Kallweit <hkallweit1@gmail.com>
To: Paul Thomas <pthomas8589@gmail.com>,
Nicolas Ferre <nicolas.ferre@microchip.com>,
Claudiu Beznea <claudiu.beznea@microchip.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
netdev@vger.kernel.org,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-riscv@lists.infradead.org
Subject: Re: net: macb: can macb use __napi_schedule_irqoff() instead of __napi_schedule()
Date: Mon, 11 Jan 2021 22:35:54 +0100 [thread overview]
Message-ID: <f3b0e354-9390-1ce8-6be5-b6ba9f201589@gmail.com> (raw)
In-Reply-To: <CAD56B7fYivPF33BhXWDPskYqNE5jRxd-sA=6+ushNXhyiCrwiQ@mail.gmail.com>
On 11.01.2021 20:45, Paul Thomas wrote:
> Hello, recently I was doing a lot of tracing/profiling to understand
> an issue we were having. Anyway, during this I ran across
> __napi_schedule_irqoff() where the comment in dev.c says "Variant of
> __napi_schedule() assuming hard irqs are masked".
>
> It looks like the queue_writel(queue, IDR, bp->rx_intr_mask); call
> just before the __napi_schedule() call in macb_main.c is doing this
> hard irq masking? So could it change to be like this?
>
It's unsafe under forced irq threading. There has been a number of
discussions about this topic in the past.
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -1616,7 +1623,7 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id)
>
> if (napi_schedule_prep(&queue->napi)) {
> netdev_vdbg(bp->dev, "scheduling RX softirq\n");
> - __napi_schedule(&queue->napi);
> + __napi_schedule_irqoff(&queue->napi);
> }
> }
>
> -Paul
>
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WARNING: multiple messages have this Message-ID (diff)
From: Heiner Kallweit <hkallweit1@gmail.com>
To: Paul Thomas <pthomas8589@gmail.com>,
Nicolas Ferre <nicolas.ferre@microchip.com>,
Claudiu Beznea <claudiu.beznea@microchip.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
netdev@vger.kernel.org,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-riscv@lists.infradead.org
Subject: Re: net: macb: can macb use __napi_schedule_irqoff() instead of __napi_schedule()
Date: Mon, 11 Jan 2021 22:35:54 +0100 [thread overview]
Message-ID: <f3b0e354-9390-1ce8-6be5-b6ba9f201589@gmail.com> (raw)
In-Reply-To: <CAD56B7fYivPF33BhXWDPskYqNE5jRxd-sA=6+ushNXhyiCrwiQ@mail.gmail.com>
On 11.01.2021 20:45, Paul Thomas wrote:
> Hello, recently I was doing a lot of tracing/profiling to understand
> an issue we were having. Anyway, during this I ran across
> __napi_schedule_irqoff() where the comment in dev.c says "Variant of
> __napi_schedule() assuming hard irqs are masked".
>
> It looks like the queue_writel(queue, IDR, bp->rx_intr_mask); call
> just before the __napi_schedule() call in macb_main.c is doing this
> hard irq masking? So could it change to be like this?
>
It's unsafe under forced irq threading. There has been a number of
discussions about this topic in the past.
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -1616,7 +1623,7 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id)
>
> if (napi_schedule_prep(&queue->napi)) {
> netdev_vdbg(bp->dev, "scheduling RX softirq\n");
> - __napi_schedule(&queue->napi);
> + __napi_schedule_irqoff(&queue->napi);
> }
> }
>
> -Paul
>
next prev parent reply other threads:[~2021-01-11 21:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 19:45 net: macb: can macb use __napi_schedule_irqoff() instead of __napi_schedule() Paul Thomas
2021-01-11 19:45 ` Paul Thomas
2021-01-11 21:35 ` Heiner Kallweit [this message]
2021-01-11 21:35 ` Heiner Kallweit
2021-01-11 22:09 ` Paul Thomas
2021-01-11 22:09 ` Paul Thomas
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