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drm: Remove utterly bogus preempt_disable() sections 

commit 27641c3f (drm/vblank: Add support for precise vblank
timestamping) adds preempt_disable()/enable() around a spin locked
section with the comments:

 * Disable preemption, so vblank_time_lock is held as short as
 * possible, even under a kernel with PREEMPT_RT patches.

/* Disable preemption while holding vblank_time_lock. Do
 * it explicitely to guard against PREEMPT_RT kernel.

Just that this has never been tested on a RT kernel which would have
granted that nonsense with a might_sleep() warning because
dev->vblank_time_lock is converted to a "sleeping" spinlock on RT.

So this is activly wrong on RT and superflous on mainline. Remove it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
hifive-unleashed-5.1
Thomas Gleixner 2011-07-23 12:45:07 +02:00 committed by Dave Airlie
parent a7c36fd8c5
commit d53dab3ae1
1 changed files with 0 additions and 9 deletions
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9
drivers/gpu/drm/drm_irq.c
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@ -110,10 +110,7 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
/* Prevent vblank irq processing while disabling vblank irqs,
* so no updates of timestamps or count can happen after we've
* disabled. Needed to prevent races in case of delayed irq's.
* Disable preemption, so vblank_time_lock is held as short as
* possible, even under a kernel with PREEMPT_RT patches.
*/
preempt_disable();
spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
dev->driver->disable_vblank(dev, crtc);
@ -164,7 +161,6 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc)
clear_vblank_timestamps(dev, crtc);
spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
preempt_enable();
}
static void vblank_disable_fn(unsigned long arg)
@ -889,10 +885,6 @@ int drm_vblank_get(struct drm_device *dev, int crtc)
spin_lock_irqsave(&dev->vbl_lock, irqflags);
/* Going from 0->1 means we have to enable interrupts again */
if (atomic_add_return(1, &dev->vblank_refcount[crtc]) == 1) {
/* Disable preemption while holding vblank_time_lock. Do
* it explicitely to guard against PREEMPT_RT kernel.
*/
preempt_disable();
spin_lock_irqsave(&dev->vblank_time_lock, irqflags2);
if (!dev->vblank_enabled[crtc]) {
/* Enable vblank irqs under vblank_time_lock protection.
@ -912,7 +904,6 @@ int drm_vblank_get(struct drm_device *dev, int crtc)
}
}
spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags2);
preempt_enable();
} else {
if (!dev->vblank_enabled[crtc]) {
atomic_dec(&dev->vblank_refcount[crtc]);