netdev - Re: [GIT PULL] virtio,vdpa,vhost: features, fixes

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Message-ID: <CACycT3ter3tB=hcTWFLboXdSsn-ZBVb8iHZCn4tv3NsnsS3TjQ@mail.gmail.com>
Date:   Sun, 12 Sep 2021 07:51:17 +0800
From:   Yongji Xie <xieyongji@...edance.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        KVM list <kvm@...r.kernel.org>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        Netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        arseny.krasnov@...persky.com, caihuoqing@...du.com,
        Eli Cohen <elic@...dia.com>, Jason Wang <jasowang@...hat.com>,
        "Zhu, Lingshan" <lingshan.zhu@...el.com>,
        Max Gurtovoy <mgurtovoy@...dia.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Will Deacon <will@...nel.org>, Wolfram Sang <wsa@...nel.org>,
        xianting.tian@...ux.alibaba.com
Subject: Re: [GIT PULL] virtio,vdpa,vhost: features, fixes

On Sun, Sep 12, 2021 at 5:56 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Thu, Sep 9, 2021 at 6:56 AM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > NB: when merging this with
> > b542e383d8c0 ("eventfd: Make signal recursion protection a task bit")
> > from Linus' tree, replace eventfd_signal_count with
> > eventfd_signal_allowed, and drop the export of eventfd_wake_count from
> > ("eventfd: Export eventfd_wake_count to modules").
>
> What? No. That can't be right.
>
> Do you mean "replace eventfd_signal_count with !eventfd_signal_allowed()"?
>
> Because if I read the logic correctly, the issue is that
> 'vduse_vq_kick()' will call eventfd_signal().
>
> Which it must not do it eventfd_signal_allowed() returns false.
>
> So if eventfd_signal_allowed() is _not_ set, the code needs to defer
> it to the workqueue.
>
> No?
>

Yes, that's my fault. I just check how the eventfd_signal_allowed()
works in fs/aio.c (also needs a fix) when I see the fix for the merge
conflicts. Sorry for that.

Thanks,
Yongji