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From:   Eric Dumazet <edumazet@google.com>
Date:   Mon, 2 Oct 2023 14:59:26 +0200
Message-ID: <CANn89iKuTLk+pWGxR36VgWUVnz2inYdqPvJP6_e8nu4TRgUO=w@mail.gmail.com>
Subject: Re: [net-next PATCH 1/3] net: introduce napi_is_scheduled helper
To:     Christian Marangi <ansuelsmth@gmail.com>
Cc:     Vincent Whitchurch <vincent.whitchurch@axis.com>,
        Raju Rangoju <rajur@chelsio.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Ping-Ke Shih <pkshih@realtek.com>,
        Kalle Valo <kvalo@kernel.org>, Simon Horman <horms@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jiri Pirko <jiri@resnulli.us>,
        Hangbin Liu <liuhangbin@gmail.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org,
        linux-wireless@vger.kernel.org
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On Mon, Oct 2, 2023 at 2:56=E2=80=AFPM Eric Dumazet <edumazet@google.com> w=
rote:
>
> On Mon, Oct 2, 2023 at 2:55=E2=80=AFPM Christian Marangi <ansuelsmth@gmai=
l.com> wrote:
> >
> > On Mon, Oct 02, 2023 at 02:49:11PM +0200, Eric Dumazet wrote:
> > > On Mon, Oct 2, 2023 at 2:43=E2=80=AFPM Christian Marangi <ansuelsmth@=
gmail.com> wrote:
> > > >
> > > > On Mon, Oct 02, 2023 at 02:35:22PM +0200, Eric Dumazet wrote:
> > > > > On Mon, Oct 2, 2023 at 2:29=E2=80=AFPM Christian Marangi <ansuels=
mth@gmail.com> wrote:
> > > > >
> > > > > > Ehhh the idea here was to reduce code duplication since the ver=
y same
> > > > > > test will be done in stmmac. So I guess this code cleanup is a =
NACK and
> > > > > > I have to duplicate the test in the stmmac driver.
> > > > >
> > > > > I simply wanted to add a comment in front of this function/helper=
,
> > > > > advising not using it unless absolutely needed.
> > > > >
> > > > > Thus my question "In which context is it safe to call this helper=
 ?"
> > > > >
> > > > > As long as it was private with a driver, I did not mind.
> > > > >
> > > > > But if made public in include/linux/netdevice.h, I would rather n=
ot
> > > > > have to explain
> > > > > to future users why it can be problematic.
> > > >
> > > > Oh ok!
> > > >
> > > > We have plenty of case similar to this. (example some clock API ver=
y
> > > > internal that should not be used normally or regmap related)
> > > >
> > > > I will include some comments warning that this should not be used i=
n
> > > > normal circumstances and other warnings. If you have suggestion on =
what
> > > > to add feel free to write them.
> > > >
> > > > Any clue on how to proceed with the sge driver?
> > > >
> > >
> > > I would remove use of this helper for something with no race ?
> > >
> > > Feel free to submit this :
> > >
> > > (Alternative would be to change napi_schedule() to return a boolean)
> > >
> >
> > Think mod napi_schedule() to return a bool would result in massive
> > warning (actually error with werror) with return value not handled.
> >
>
> It should not, unless we added a __must_check

This was what I was thinking :

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e070a4540fbaf4a9cf310d5f53c4401840c72776..6aa2bc315411d1a0f7db314f1fb=
fb11aae7c31fe
100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -491,10 +491,13 @@ bool napi_schedule_prep(struct napi_struct *n);
  * Schedule NAPI poll routine to be called if it is not already
  * running.
  */
-static inline void napi_schedule(struct napi_struct *n)
+static inline bool napi_schedule(struct napi_struct *n)
 {
-       if (napi_schedule_prep(n))
+       if (napi_schedule_prep(n)) {
                __napi_schedule(n);
+               return true;
+       }
+       return false;
 }

 /**