linux-kernel - Re: [PATCH net 2/2] net: ipa: re-enable NAPI before enabling interrupt

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Message-ID: <20210107183803.47308e23@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 7 Jan 2021 18:38:03 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Alex Elder <elder@...aro.org>
Cc:     davem@...emloft.net, evgreen@...omium.org,
        bjorn.andersson@...aro.org, cpratapa@...eaurora.org,
        subashab@...eaurora.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 2/2] net: ipa: re-enable NAPI before enabling
 interrupt

On Thu,  7 Jan 2021 15:43:25 -0600 Alex Elder wrote:
> @@ -743,21 +743,21 @@ static void gsi_channel_freeze(struct gsi_channel *channel)
>  	set_bit(GSI_CHANNEL_FLAG_STOPPING, channel->flags);
>  	smp_mb__after_atomic();	/* Ensure gsi_channel_poll() sees new value */
>  
> -	napi_disable(&channel->napi);
> -
>  	gsi_irq_ieob_disable(channel->gsi, channel->evt_ring_id);
> +
> +	napi_disable(&channel->napi);
>  }

So patch 1 is entirely for the purpose of keeping the code symmetric
here? I can't think of other reason why masking this IRQ couldn't be
left after NAPI is disabled, and that should work as you expect.

>  /* Allow transactions to be used on the channel again. */
>  static void gsi_channel_thaw(struct gsi_channel *channel)
>  {
> -	gsi_irq_ieob_enable(channel->gsi, channel->evt_ring_id);
> -
>  	/* Allow the NAPI poll loop to re-enable interrupts again */
>  	clear_bit(GSI_CHANNEL_FLAG_STOPPING, channel->flags);
>  	smp_mb__after_atomic();	/* Ensure gsi_channel_poll() sees new value */
>  
>  	napi_enable(&channel->napi);
> +
> +	gsi_irq_ieob_enable(channel->gsi, channel->evt_ring_id);
>  }