linux-kernel - Re: [PATCH net v1] octeontx2-pf: Fix page pool cache index corruption.

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Message-ID: <20230906080831.k5HXMqlN@linutronix.de>
Date:   Wed, 6 Sep 2023 10:08:31 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Ratheesh Kannoth <rkannoth@...vell.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        sgoutham@...vell.com, gakula@...vell.com, sbhatta@...vell.com,
        hkelam@...vell.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, hawk@...nel.org,
        alexander.duyck@...il.com, ilias.apalodimas@...aro.org,
        linyunsheng@...wei.com
Subject: Re: [PATCH net v1] octeontx2-pf: Fix page pool cache index
 corruption.

On 2023-09-06 09:09:26 [+0530], Ratheesh Kannoth wrote:
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> index 8511906cb4e2..5bba1f34e4f6 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
> @@ -1082,38 +1070,16 @@ static int otx2_cq_init(struct otx2_nic *pfvf, u16 qidx)
>  static void otx2_pool_refill_task(struct work_struct *work)
>  {
…
> +	napi_schedule(wrk->napi);

This will delay NAPI until "some random point in the future" for
instance if an interrupt on _this_ CPU fires. You only set the softirq
state and never enforce it here. This works as intended if invoked from
an IRQ but this here a worker/ process context.

You can either put local_bh_disable()/enable() around napi_schedule() or
use it from a timer callback and skip the worker.

Sebastian