linux-kernel - Re: [PATCH] drm/vkms: add missing drm_crtc_vblank_put to the get/put pair on flush

Open Source and information security mailing list archives

Date:   Sat, 25 Jul 2020 16:19:46 -0300
From:   Melissa Wen <melissa.srw@...il.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Sidong Yang <realwakka@...il.com>,
        Haneen Mohammed <hamohammed.sa@...il.com>,
        Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        kernel-usp@...glegroups.com
Subject: Re: [PATCH] drm/vkms: add missing drm_crtc_vblank_put to the get/put
 pair on flush

> No, this very first warning continues (only once) :(
> From here (drm_crtc_vblank_on):
>         if (atomic_read(&vblank->refcount) != 0 || drm_vblank_offdelay == 0)
>                 drm_WARN_ON(dev, drm_vblank_enable(dev, pipe));

Sorry, not sure when this warning is triggered.

>
> > But I'm still wondering why after step 3 we don't get -EINVAL from
> > vblank_get() - after vblank_off() vblank->enabled should be false
> > again, getting us back to the same state as after 1. Is that not
> > happening?
>
> Yes (sorry if it got confused), we got -EINVAL after setp 3:
>
> In step 3, at the end of the 2nd running, we have:
> atomic_disable
> --> vblank_off [!vblank->inmodeset + refcount going 0->1 + inmodeset=1]
> and then in next vblank_get: -EINVAL (!vblank->enabled + refcount ends 1)
> as in the first step.
>
> Melissa
>
> > -Daniel
> >
> > >
> > > > >
> > > > > Thanks
> > > > > -Sidong
> > > > >
> > > > > > > >
> > > > > > > > >             crtc->state->event = NULL;
> > > > > > > > >     }
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > > 2.27.0
> > > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > Daniel Vetter
> > > > > > > > Software Engineer, Intel Corporation
> > > > > > > > http://blog.ffwll.ch
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Daniel Vetter
> > > > > > Software Engineer, Intel Corporation
> > > > > > http://blog.ffwll.ch
> > > > > > _______________________________________________
> > > > > > dri-devel mailing list
> > > > > > dri-devel@...ts.freedesktop.org
> > > > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > > >
> > > >
> > > >
> > > > --
> > > > Daniel Vetter
> > > > Software Engineer, Intel Corporation
> > > > http://blog.ffwll.ch
> >
> >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch

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