From: Daniel Vetter Date: Sun, 3 Nov 2013 19:27:05 +0000 (+0100) Subject: drm/irq: remove cargo-culted locking from irq_install/uninstall X-Git-Tag: next-20140502~52^2^2~13 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=e090c53b21e97864a25ada5c8437d9776978a050;p=karo-tx-linux.git drm/irq: remove cargo-culted locking from irq_install/uninstall The dev->struct_mutex locking in drm_irq.c only protects dev->irq_enabled. Which isn't really much at all and only prevents especially nasty ums userspace from concurrently installing the interrupt handling a few times. Or at least trying. There are tons of unlocked readers of dev->irqs_enabled in the vblank wait code (and by extension also in the pageflip code since that uses the same vblank timestamp engine). Real modesetting drivers should ensure that nothing can go haywire with a sane setup teardown sequence. So we only really need this for the drm_control ioctl, everywhere else this will just paper over nastiness. Note that drm/i915 is a bit specially due to the gem+ums combination. So there we also need to properly protect the entervt and leavevt ioctls. But it's definitely saner to do everything in one go than to drop the lock in-between. Finally there's the gpu reset code in drm/i915. That one's just race (concurrent userspace calls to for vblank waits of pageflips could spuriously fail). So wrap it up in with a nice comment since fixing this is more involved. v2: Rebase and fix commit message (Thierry) Reviewed-by: Thierry Reding Reviewed-by: Laurent Pinchart Signed-off-by: Daniel Vetter --- diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 580f9ed2dca6..06a53f8b618c 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -254,20 +254,13 @@ int drm_irq_install(struct drm_device *dev) if (drm_dev_to_irq(dev) == 0) return -EINVAL; - mutex_lock(&dev->struct_mutex); - /* Driver must have been initialized */ - if (!dev->dev_private) { - mutex_unlock(&dev->struct_mutex); + if (!dev->dev_private) return -EINVAL; - } - if (dev->irq_enabled) { - mutex_unlock(&dev->struct_mutex); + if (dev->irq_enabled) return -EBUSY; - } dev->irq_enabled = true; - mutex_unlock(&dev->struct_mutex); DRM_DEBUG("irq=%d\n", drm_dev_to_irq(dev)); @@ -288,9 +281,7 @@ int drm_irq_install(struct drm_device *dev) sh_flags, irqname, dev); if (ret < 0) { - mutex_lock(&dev->struct_mutex); dev->irq_enabled = false; - mutex_unlock(&dev->struct_mutex); return ret; } @@ -302,9 +293,7 @@ int drm_irq_install(struct drm_device *dev) ret = dev->driver->irq_postinstall(dev); if (ret < 0) { - mutex_lock(&dev->struct_mutex); dev->irq_enabled = false; - mutex_unlock(&dev->struct_mutex); if (!drm_core_check_feature(dev, DRIVER_MODESET)) vga_client_register(dev->pdev, NULL, NULL, NULL); free_irq(drm_dev_to_irq(dev), dev); @@ -330,10 +319,8 @@ int drm_irq_uninstall(struct drm_device *dev) if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ)) return -EINVAL; - mutex_lock(&dev->struct_mutex); irq_enabled = dev->irq_enabled; dev->irq_enabled = false; - mutex_unlock(&dev->struct_mutex); /* * Wake up any waiters so they don't hang. @@ -381,6 +368,7 @@ int drm_control(struct drm_device *dev, void *data, struct drm_file *file_priv) { struct drm_control *ctl = data; + int ret = 0; /* if we haven't irq we fallback for compatibility reasons - * this used to be a separate function in drm_dma.h @@ -399,9 +387,17 @@ int drm_control(struct drm_device *dev, void *data, if (dev->if_version < DRM_IF_VERSION(1, 2) && ctl->irq != drm_dev_to_irq(dev)) return -EINVAL; - return drm_irq_install(dev); + mutex_lock(&dev->struct_mutex); + ret = drm_irq_install(dev); + mutex_unlock(&dev->struct_mutex); + + return ret; case DRM_UNINST_HANDLER: - return drm_irq_uninstall(dev); + mutex_lock(&dev->struct_mutex); + ret = drm_irq_uninstall(dev); + mutex_unlock(&dev->struct_mutex); + + return ret; default: return -EINVAL; } diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c index 82f4d1f47d3b..87ce105910f2 100644 --- a/drivers/gpu/drm/i915/i915_drv.c +++ b/drivers/gpu/drm/i915/i915_drv.c @@ -746,6 +746,11 @@ int i915_reset(struct drm_device *dev) return ret; } + /* + * FIXME: This is horribly race against concurrent pageflip and + * vblank wait ioctls since they can observe dev->irqs_disabled + * being false when they shouldn't be able to. + */ drm_irq_uninstall(dev); drm_irq_install(dev); diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 2871ce75f438..d2cc19a7023f 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -4522,16 +4522,15 @@ i915_gem_entervt_ioctl(struct drm_device *dev, void *data, } BUG_ON(!list_empty(&dev_priv->gtt.base.active_list)); - mutex_unlock(&dev->struct_mutex); ret = drm_irq_install(dev); if (ret) goto cleanup_ringbuffer; + mutex_unlock(&dev->struct_mutex); return 0; cleanup_ringbuffer: - mutex_lock(&dev->struct_mutex); i915_gem_cleanup_ringbuffer(dev); dev_priv->ums.mm_suspended = 1; mutex_unlock(&dev->struct_mutex); @@ -4546,7 +4545,9 @@ i915_gem_leavevt_ioctl(struct drm_device *dev, void *data, if (drm_core_check_feature(dev, DRIVER_MODESET)) return 0; + mutex_lock(&dev->struct_mutex); drm_irq_uninstall(dev); + mutex_unlock(&dev->struct_mutex); return i915_gem_suspend(dev); }