netdev - Re: [net-next PATCH v2 4/4] netdev: use napi_schedule bool instead of napi_schedule_prep/__napi

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Message-ID: <CANn89iLtYZJPOQE7OkAbEdmhT8qjzAJ+27poa__3c8Nf0M6u_w@mail.gmail.com>
Date: Thu, 5 Oct 2023 18:16:26 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>, 
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Subject: Re: [net-next PATCH v2 4/4] netdev: use napi_schedule bool instead of napi_schedule_prep/__napi_schedule

On Tue, Oct 3, 2023 at 8:36 PM Christian Marangi <ansuelsmth@...il.com> wrote:
>
> Replace if condition of napi_schedule_prep/__napi_schedule and use bool
> from napi_schedule directly where possible.
>
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> ---
>  drivers/net/ethernet/atheros/atlx/atl1.c     | 4 +---
>  drivers/net/ethernet/toshiba/tc35815.c       | 4 +---
>  drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 4 +---
>  3 files changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/ethernet/atheros/atlx/atl1.c b/drivers/net/ethernet/atheros/atlx/atl1.c
> index 02aa6fd8ebc2..a9014d7932db 100644
> --- a/drivers/net/ethernet/atheros/atlx/atl1.c
> +++ b/drivers/net/ethernet/atheros/atlx/atl1.c
> @@ -2446,7 +2446,7 @@ static int atl1_rings_clean(struct napi_struct *napi, int budget)
>
>  static inline int atl1_sched_rings_clean(struct atl1_adapter* adapter)
>  {
> -       if (!napi_schedule_prep(&adapter->napi))
> +       if (!napi_schedule(&adapter->napi))
>                 /* It is possible in case even the RX/TX ints are disabled via IMR
>                  * register the ISR bits are set anyway (but do not produce IRQ).
>                  * To handle such situation the napi functions used to check is
> @@ -2454,8 +2454,6 @@ static inline int atl1_sched_rings_clean(struct atl1_adapter* adapter)
>                  */
>                 return 0;
>
> -       __napi_schedule(&adapter->napi);
> -
>         /*
>          * Disable RX/TX ints via IMR register if it is
>          * allowed. NAPI handler must reenable them in same
> diff --git a/drivers/net/ethernet/toshiba/tc35815.c b/drivers/net/ethernet/toshiba/tc35815.c
> index 14cf6ecf6d0d..a8b8a0e13f9a 100644
> --- a/drivers/net/ethernet/toshiba/tc35815.c
> +++ b/drivers/net/ethernet/toshiba/tc35815.c
> @@ -1436,9 +1436,7 @@ static irqreturn_t tc35815_interrupt(int irq, void *dev_id)
>         if (!(dmactl & DMA_IntMask)) {
>                 /* disable interrupts */
>                 tc_writel(dmactl | DMA_IntMask, &tr->DMA_Ctl);
> -               if (napi_schedule_prep(&lp->napi))
> -                       __napi_schedule(&lp->napi);
> -               else {
> +               if (!napi_schedule(&lp->napi)) {
>                         printk(KERN_ERR "%s: interrupt taken in poll\n",
>                                dev->name);
>                         BUG();

Hmmm... could you also remove this BUG() ? I think this code path can be taken
if some applications are using busy polling.

Or simply rewrite this with the traditional

if (napi_schedule_prep(&lp->napi)) {
   /* disable interrupts */
   tc_writel(dmactl | DMA_IntMask, &tr->DMA_Ctl);
    __napi_schedule(&lp->napi);
}



> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
> index 23b5a0adcbd6..146bc7bd14fb 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
> @@ -1660,9 +1660,7 @@ irqreturn_t iwl_pcie_irq_rx_msix_handler(int irq, void *dev_id)
>         IWL_DEBUG_ISR(trans, "[%d] Got interrupt\n", entry->entry);
>
>         local_bh_disable();
> -       if (napi_schedule_prep(&rxq->napi))
> -               __napi_schedule(&rxq->napi);
> -       else
> +       if (!napi_schedule(&rxq->napi))
>                 iwl_pcie_clear_irq(trans, entry->entry);

Same remark here about twisted logic.

>         local_bh_enable();
>
> --
> 2.40.1
>