From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 1/9] drm: Always reject drm_vblank_get() after drm_vblank_off() Date: Mon, 26 May 2014 15:21:41 +0200 Message-ID: <20140526132141.GI14357@phenom.ffwll.local> References: <1401104792-26560-1-git-send-email-ville.syrjala@linux.intel.com> <1401104792-26560-2-git-send-email-ville.syrjala@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <1401104792-26560-2-git-send-email-ville.syrjala@linux.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: ville.syrjala@linux.intel.com Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org On Mon, May 26, 2014 at 02:46:24PM +0300, ville.syrjala@linux.intel.com wro= te: > From: Ville Syrj=E4l=E4 > = > Make sure drm_vblank_get() never succeeds when called between > drm_vblank_off() and drm_vblank_on(). Borrow a trick from the > old drm_vblank_{pre,post}_modeset() functions and just bump > the refcount in drm_vblank_off() and drop it in drm_vblank_on(). > = > Hopefully the use of inmodeset won't conflict badly with > drm_vblank_{pre,post}_modeset(). > = > For i915 there's a window between drm_vblank_off() and marking the > crtc as inactive where the current code still allows drm_vblank_get(). > = > Signed-off-by: Ville Syrj=E4l=E4 Afaics we never check anywhere for inmodeset in drm_vblank_get, so how does this work? -Daniel > --- > drivers/gpu/drm/drm_irq.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > = > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c > index b565372..7b1e08c 100644 > --- a/drivers/gpu/drm/drm_irq.c > +++ b/drivers/gpu/drm/drm_irq.c > @@ -1039,6 +1039,15 @@ void drm_vblank_off(struct drm_device *dev, int cr= tc) > } > spin_unlock(&dev->event_lock); > = > + /* > + * Prevent subsequent drm_vblank_get() from re-enabling > + * the vblank interrupt by bumping the refcount. > + */ > + if (!dev->vblank[crtc].inmodeset) { > + atomic_inc(&dev->vblank[crtc].refcount); > + dev->vblank[crtc].inmodeset =3D 1; > + } > + > spin_unlock_irqrestore(&dev->vbl_lock, irqflags); > } > EXPORT_SYMBOL(drm_vblank_off); > @@ -1079,6 +1088,11 @@ void drm_vblank_on(struct drm_device *dev, int crt= c) > unsigned long irqflags; > = > spin_lock_irqsave(&dev->vbl_lock, irqflags); > + /* Drop our private "prevent drm_vblank_get" refcount */ > + if (dev->vblank[crtc].inmodeset) { > + atomic_dec(&dev->vblank[crtc].refcount); > + dev->vblank[crtc].inmodeset =3D 0; > + } > /* re-enable interrupts if there's are users left */ > if (atomic_read(&dev->vblank[crtc].refcount) !=3D 0) > WARN_ON(drm_vblank_enable(dev, crtc)); > -- = > 1.8.5.5 > = > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- = Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch