linux-kernel - Re: [PATCH] net: macb: Change interrupt and napi enable order in open

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Message-Id: <20190507.122849.1270099594432351727.davem@davemloft.net>
Date:   Tue, 07 May 2019 12:28:49 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     harini.katakam@...inx.com
Cc:     nicolas.ferre@...rochip.com, rafalo@...ence.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        michal.simek@...inx.com, harinikatakamlinux@...il.com
Subject: Re: [PATCH] net: macb: Change interrupt and napi enable order in
 open

From: Harini Katakam <harini.katakam@...inx.com>
Date: Tue, 7 May 2019 19:59:10 +0530

> Current order in open:
> -> Enable interrupts (macb_init_hw)
> -> Enable NAPI
> -> Start PHY
> 
> Sequence of RX handling:
> -> RX interrupt occurs
> -> Interrupt is cleared and interrupt bits disabled in handler
> -> NAPI is scheduled
> -> In NAPI, RX budget is processed and RX interrupts are re-enabled
> 
> With the above, on QEMU or fixed link setups (where PHY state doesn't
> matter), there's a chance macb RX interrupt occurs before NAPI is
> enabled. This will result in NAPI being scheduled before it is enabled.
> Fix this macb open by changing the order.
> 
> Fixes: ae1f2a56d273 ("net: macb: Added support for many RX queues")
> Signed-off-by: Harini Katakam <harini.katakam@...inx.com>

Applied and queued up for -stable.