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From:   Yejune Deng <yejune.deng@gmail.com>
Date:   Fri, 11 Dec 2020 10:43:54 +0800
Message-ID: <CABWKuGVvh93zNYky_Lj2Hyenoerm+PBj38ocfYcw0k0_en=7Lg@mail.gmail.com>
Subject: Re: [PATCH] net: core: fix msleep() is not accurate
To:     Eric Dumazet <edumazet@google.com>
Cc:     David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andriin@fb.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Taehee Yoo <ap420073@gmail.com>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Jiri Pirko <jiri@mellanox.com>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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Does anyone else have a different opinion? If not=EF=BC=8CI will adopt it a=
nd resubmit.

On Thu, Dec 10, 2020 at 6:19 PM Eric Dumazet <edumazet@google.com> wrote:
>
> On Thu, Dec 10, 2020 at 10:35 AM Yejune Deng <yejune.deng@gmail.com> wrot=
e:
> >
> > See Documentation/timers/timers-howto.rst, msleep() is not
> > for (1ms - 20ms), There is a more advanced API is used.
> >
> > Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
> > ---
> >  net/core/dev.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index d33099f..6e83ee03 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -6726,9 +6726,9 @@ void napi_disable(struct napi_struct *n)
> >         set_bit(NAPI_STATE_DISABLE, &n->state);
> >
> >         while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
> > -               msleep(1);
> > +               fsleep(1000);
> >         while (test_and_set_bit(NAPI_STATE_NPSVC, &n->state))
> > -               msleep(1);
> > +               fsleep(1000);
> >
>
> I would prefer explicit usleep_range().
>
> fsleep() is not common in the kernel, I had to go to its definition.
>
> I would argue that we should  use usleep_range(10, 200)  to have an
> opportunity to spend less time in napi_disable() in some cases.