From: Tvrtko Ursulin tvrtko.ursulin@intel.com
We had two failure modes here:
1. Deadlock in intelfb_alloc failure path where it calls drm_framebuffer_remove, which grabs the struct mutex and intelfb_create (caller of intelfb_alloc) was already holding it.
2. Deadlock in intelfb_create failure path where it calls drm_framebuffer_unreference, which grabs the struct mutex and intelfb_create was already holding it.
v2: * Reformat commit msg to 72 chars. (Lukas Wunner) * Add third failure mode. (Lukas Wunner)
v3: * On fb alloc failure, unref gem object where it gets refed, fix double unref in separate commit. (Ville Syrjälä)
v4: * Lock struct mutex on unref. (Chris Wilson)
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=88861 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=61115 Tested-by: Paul Hordiienko pvt.gord@gmail.com [MBP 6,2 2010 intel ILK + nvidia GT216 pre-retina] Tested-by: William Brown william@blackhats.net.au [MBP 8,2 2011 intel SNB + amd turks pre-retina] Tested-by: Lukas Wunner lukas@wunner.de [MBP 9,1 2012 intel IVB + nvidia GK107 pre-retina] Tested-by: Bruno Bierbaumer bruno@bierbaumer.net [MBP 11,3 2013 intel HSW + nvidia GK107 retina -- work in progress]
Signed-off-by: Tvrtko Ursulin tvrtko.ursulin@intel.com Fixes: 60a5ca015ffd ("drm/i915: Add locking around framebuffer_references--") Reported-by: Lukas Wunner lukas@wunner.de [Lukas: Create v3 + v4 based on Tvrtko's v2] Signed-off-by: Lukas Wunner lukas@wunner.de Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Ville Syrjälä ville.syrjala@linux.intel.com --- drivers/gpu/drm/i915/intel_fbdev.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c index 7eff33f..dd138aa 100644 --- a/drivers/gpu/drm/i915/intel_fbdev.c +++ b/drivers/gpu/drm/i915/intel_fbdev.c @@ -140,7 +140,7 @@ static int intelfb_alloc(struct drm_fb_helper *helper, { struct intel_fbdev *ifbdev = container_of(helper, struct intel_fbdev, helper); - struct drm_framebuffer *fb; + struct drm_framebuffer *fb = NULL; struct drm_device *dev = helper->dev; struct drm_mode_fb_cmd2 mode_cmd = {}; struct drm_i915_gem_object *obj; @@ -158,6 +158,8 @@ static int intelfb_alloc(struct drm_fb_helper *helper, mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
+ mutex_lock(&dev->struct_mutex); + size = mode_cmd.pitches[0] * mode_cmd.height; size = PAGE_ALIGN(size); obj = i915_gem_object_create_stolen(dev, size); @@ -179,18 +181,21 @@ static int intelfb_alloc(struct drm_fb_helper *helper, ret = intel_pin_and_fence_fb_obj(NULL, fb, NULL, NULL, NULL); if (ret) { DRM_ERROR("failed to pin obj: %d\n", ret); - goto out_fb; + goto out_unref; }
+ mutex_unlock(&dev->struct_mutex); + ifbdev->fb = to_intel_framebuffer(fb);
return 0;
-out_fb: - drm_framebuffer_remove(fb); out_unref: drm_gem_object_unreference(&obj->base); out: + mutex_unlock(&dev->struct_mutex); + if (fb) + drm_framebuffer_remove(fb); return ret; }
@@ -208,8 +213,6 @@ static int intelfb_create(struct drm_fb_helper *helper, int size, ret; bool prealloc = false;
- mutex_lock(&dev->struct_mutex); - if (intel_fb && (sizes->fb_width > intel_fb->base.width || sizes->fb_height > intel_fb->base.height)) { @@ -224,7 +227,7 @@ static int intelfb_create(struct drm_fb_helper *helper, DRM_DEBUG_KMS("no BIOS fb, allocating a new one\n"); ret = intelfb_alloc(helper, sizes); if (ret) - goto out_unlock; + return ret; intel_fb = ifbdev->fb; } else { DRM_DEBUG_KMS("re-using BIOS fb\n"); @@ -236,6 +239,8 @@ static int intelfb_create(struct drm_fb_helper *helper, obj = intel_fb->obj; size = obj->base.size;
+ mutex_lock(&dev->struct_mutex); + info = framebuffer_alloc(0, &dev->pdev->dev); if (!info) { ret = -ENOMEM; @@ -306,7 +311,6 @@ static int intelfb_create(struct drm_fb_helper *helper, out_unpin: i915_gem_object_ggtt_unpin(obj); drm_gem_object_unreference(&obj->base); -out_unlock: mutex_unlock(&dev->struct_mutex); return ret; }