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From:   Brian Norris <briannorris@chromium.org>
Date:   Thu, 15 Aug 2019 14:11:10 -0700
Message-ID: <CA+ASDXPJiNTXAihzohT06RS57gkJU9Q-u3kpp0piJP-3U1miFw@mail.gmail.com>
Subject: Re: [PATCH v3 2/3] rtw88: enclose c2h cmd handle with mutex
To:     Tony Chuang <yhchuang@realtek.com>
Cc:     Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        Stanislaw Gruszka <sgruszka@redhat.com>
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I understand this is already queued up, but I still have a question:

On Wed, Jul 31, 2019 at 5:23 AM <yhchuang@realtek.com> wrote:
> C2H commands that cannot be handled in IRQ context should
> be protected by rtwdev->mutex. Because they might have a
> sequece of hardware operations that does not want to be
> interfered.

Can you elaborate on what interference you're looking at, exactly? I'm
not a big fan of defensive addition of global locks, and this
particular mutex isn't very targeted. It claims to be for mac80211
callbacks, but you use it in quite a few places (some of which clearly
don't make sense), and many of them are not related to mac80211
callbacks AFAICT.

To the contrary: this handler is called from the mac80211 work queue,
which is ordered and therefore shouldn't be getting "interrupted"
(e.g., conflicting commands). But then, you added the 'irqsafe'
command, which gets run from the ISR...and doesn't hold this lock,
obviously.

It may well be that you're correct here, but I'd like to see a better
explanation for stuff like this. And maybe an update to the
rtw_dev::mutex comments.

Brian