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From:   Brian Norris <briannorris@chromium.org>
Date:   Fri, 29 Jan 2021 15:39:08 -0800
Message-ID: <CA+ASDXM7e4eSiJNoVMES7=mZ3M-NGpVZ9jLbjNm4yqMSYH4r+Q@mail.gmail.com>
Subject: Re: [PATCH v4 3/8] rtw88: add napi support
To:     Pkshih <pkshih@realtek.com>
Cc:     Yan-Hsuan Chuang <tony0620emma@gmail.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        Bernie Huang <phhuang@realtek.com>
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On Thu, Jan 28, 2021 at 1:45 AM Pkshih <pkshih@realtek.com> wrote:
> > -----Original Message-----
> > From: Brian Norris [mailto:briannorris@chromium.org]
> > On Fri, Jan 15, 2021 at 1:26 AM Ping-Ke Shih <pkshih@realtek.com> wrote:
> > > +static u32 rtw_pci_rx_napi(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
> > >                            u8 hw_queue)
> > ...
> >
> > Are you sure you don't want any locking in rtw_pci_rx_napi()?
> > Previously, you held irq_lock for the entirety of rtw_pci_rx_isr(),
> > but now all the RX work is being deferred to a NAPI context, without
> > any additional lock. IIUC, that means you can be both handling RX and
> > other ISR operations at the same time. Is that intentional?
> >
>
> irq_lock is used to protect TX ring->queue. The TX skb(s) are queued into the
> queue, and unlink the skb until TX_OK_ISR is received. So, RX doesn't need to
> hold this lock.

I could be misunderstanding your locking model, but IIUC, you're left
with zero locking between NAPI RX and all other operations (H2C, link
up/down -- including DMA free, etc.). irq_lock used to protect you
from that.

If I'm right, maybe it needs a rename and/or some additional comments.

Brian