On Mon, 22 Jun 2015, Josh Boyer jwboyer@fedoraproject.org wrote:
On Mon, Jun 22, 2015 at 8:02 AM, Daniel Vetter daniel.vetter@ffwll.ch wrote:
We should never nest these since in theory kms drivers should know when a pipe is on/off and call the corresponding enable/disable functions for the vblank helper code only once. But for historical reasons (the shared-with-ums version of this code in modeset_pre/post needed to be able to cope with silly userspace that lost track of things) we still have this bit of "robustness" around.
Enforce this with a WARN_ON, preparing to eventually rip out this special handling.
This doesn't really provide any context in the WARN_ON itself. It will just result in a splat that looks like a kernel oops, and end users and distribution maintainers will be left scratching their heads.
Could this be done with a printk warning instead, or could you at least provide a pr_warn statement to help people understand why their machine has an oops splat?
FWIW i915_drv.h has
#define WARN_ON(x) WARN((x), "WARN_ON(" #x ")")
which makes it a little better...
BR, Jani.
josh
Cc: Yogesh Mohan Marimuthu yogesh.mohan.marimuthu@intel.com Cc: Gaurav K Singh gaurav.k.singh@intel.com Cc: Michel Dänzer michel.daenzer@amd.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Signed-off-by: Daniel Vetter daniel.vetter@intel.com
drivers/gpu/drm/drm_irq.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index f9cc68fbd2a3..3819465abe22 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1219,6 +1219,8 @@ void drm_vblank_off(struct drm_device *dev, int crtc) vblank_disable_and_save(dev, crtc); wake_up(&vblank->queue);
WARN_ON(vblank->inmodeset);/* * Prevent subsequent drm_vblank_get() from re-enabling * the vblank interrupt by bumping the refcount.@@ -1318,6 +1320,8 @@ void drm_vblank_on(struct drm_device *dev, int crtc) return;
spin_lock_irqsave(&dev->vbl_lock, irqflags);
WARN_ON(!vblank->inmodeset);/* Drop our private "prevent drm_vblank_get" refcount */ if (vblank->inmodeset) { atomic_dec(&vblank->refcount);-- 2.1.4
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