| Message ID | 20200624230318.126256-3-lyude@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/nouveau: Introduce CRC support for gf119+ | expand |
On Wed, Jun 24, 2020 at 07:03:09PM -0400, Lyude Paul wrote: > This got me confused for a bit while looking over this code: I had been > planning on adding some blocking function calls into this function, but > seeing the irqsave/irqrestore variants of spin_(un)lock() didn't make it > very clear whether or not that would actually be safe. > > So I went ahead and reviewed every single driver in the kernel that uses > this function, and they all fall into three categories: > > * Driver probe code > * ->atomic_disable() callbacks > * Legacy modesetting callbacks > > All of these will be guaranteed to have IRQs enabled, which means it's > perfectly safe to block here. Just to make things a little less > confusing to others in the future, let's switch over to > spin_lock_irq()/spin_unlock_irq() to make that fact a little more > obvious. > > Signed-off-by: Lyude Paul <lyude@redhat.com> > Cc: Daniel Vetter <daniel@ffwll.ch> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> I think the patch is correct, but now we're having a bit a inconsistency, since all other functions where the same applies still use _irqsave. I looked through the file and I think drm_vblank_get, drm_crtc_vblank_reset, drm_crtc_vblank_on and drm_legacy_vblank_post_modeset, drm_queue_vblank_event and drm_crtc_queue_sequence_ioctl are all candiates for the same cleanup. Maybe follow up patches for less confusion? On this: Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> > --- > drivers/gpu/drm/drm_vblank.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > index ce5c1e1d29963..e895f5331fdb4 100644 > --- a/drivers/gpu/drm/drm_vblank.c > +++ b/drivers/gpu/drm/drm_vblank.c > @@ -1283,13 +1283,12 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc) > struct drm_pending_vblank_event *e, *t; > > ktime_t now; > - unsigned long irqflags; > u64 seq; > > if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) > return; > > - spin_lock_irqsave(&dev->event_lock, irqflags); > + spin_lock_irq(&dev->event_lock); > > spin_lock(&dev->vbl_lock); > drm_dbg_vbl(dev, "crtc %d, vblank enabled %d, inmodeset %d\n", > @@ -1325,7 +1324,7 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc) > drm_vblank_put(dev, pipe); > send_vblank_event(dev, e, seq, now); > } > - spin_unlock_irqrestore(&dev->event_lock, irqflags); > + spin_unlock_irq(&dev->event_lock); > > /* Will be reset by the modeset helpers when re-enabling the crtc by > * calling drm_calc_timestamping_constants(). */ > -- > 2.26.2 >
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index ce5c1e1d29963..e895f5331fdb4 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1283,13 +1283,12 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc) struct drm_pending_vblank_event *e, *t; ktime_t now; - unsigned long irqflags; u64 seq; if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) return; - spin_lock_irqsave(&dev->event_lock, irqflags); + spin_lock_irq(&dev->event_lock); spin_lock(&dev->vbl_lock); drm_dbg_vbl(dev, "crtc %d, vblank enabled %d, inmodeset %d\n", @@ -1325,7 +1324,7 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc) drm_vblank_put(dev, pipe); send_vblank_event(dev, e, seq, now); } - spin_unlock_irqrestore(&dev->event_lock, irqflags); + spin_unlock_irq(&dev->event_lock); /* Will be reset by the modeset helpers when re-enabling the crtc by * calling drm_calc_timestamping_constants(). */
This got me confused for a bit while looking over this code: I had been planning on adding some blocking function calls into this function, but seeing the irqsave/irqrestore variants of spin_(un)lock() didn't make it very clear whether or not that would actually be safe. So I went ahead and reviewed every single driver in the kernel that uses this function, and they all fall into three categories: * Driver probe code * ->atomic_disable() callbacks * Legacy modesetting callbacks All of these will be guaranteed to have IRQs enabled, which means it's perfectly safe to block here. Just to make things a little less confusing to others in the future, let's switch over to spin_lock_irq()/spin_unlock_irq() to make that fact a little more obvious. Signed-off-by: Lyude Paul <lyude@redhat.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> --- drivers/gpu/drm/drm_vblank.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)