diff options
author | Chris Wilson <chris@chris-wilson.co.uk> | 2010-11-08 01:12:29 +0000 |
---|---|---|
committer | Chris Wilson <chris@chris-wilson.co.uk> | 2010-11-08 09:19:11 +0000 |
commit | b47b30ccdaad5f2fc39a1a65921bffd150574a91 (patch) | |
tree | 9eaef1721b05daa71010de638e02b2e6b4850598 /drivers/gpu | |
parent | 16a02cf08a2de0863daf7ebb91718d7c6bbe7f9c (diff) |
drm/i915: Avoid might_fault during pwrite whilst holding our mutex
... and so prevent a potential circular reference:
[ INFO: possible circular locking dependency detected ]
2.6.37-rc1-uwe1+ #4
-------------------------------------------------------
Xorg/1401 is trying to acquire lock:
(&mm->mmap_sem){++++++}, at: [<c01e4ddb>] might_fault+0x4b/0xa0
but task is already holding lock:
(&dev->struct_mutex){+.+.+.}, at: [<f869c3ac>]
i915_mutex_lock_interruptible+0x3c/0x60 [i915]
which lock already depends on the new lock.
When the locking around the pwrite ioctl was simplified, I did not spot
that the phys path never took any locks and so we introduced this
potential circular reference.
Reported-by: Uwe Helm <uwe.helm@googlemail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Diffstat (limited to 'drivers/gpu')
-rw-r--r-- | drivers/gpu/drm/i915/i915_gem.c | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 984eb6e9db0..eba9b161522 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -4878,17 +4878,24 @@ i915_gem_phys_pwrite(struct drm_device *dev, struct drm_gem_object *obj, struct drm_file *file_priv) { struct drm_i915_gem_object *obj_priv = to_intel_bo(obj); - void *obj_addr; - int ret; - char __user *user_data; + void *vaddr = obj_priv->phys_obj->handle->vaddr + args->offset; + char __user *user_data = (char __user *) (uintptr_t) args->data_ptr; - user_data = (char __user *) (uintptr_t) args->data_ptr; - obj_addr = obj_priv->phys_obj->handle->vaddr + args->offset; + DRM_DEBUG_DRIVER("vaddr %p, %lld\n", vaddr, args->size); - DRM_DEBUG_DRIVER("obj_addr %p, %lld\n", obj_addr, args->size); - ret = copy_from_user(obj_addr, user_data, args->size); - if (ret) - return -EFAULT; + if (__copy_from_user_inatomic_nocache(vaddr, user_data, args->size)) { + unsigned long unwritten; + + /* The physical object once assigned is fixed for the lifetime + * of the obj, so we can safely drop the lock and continue + * to access vaddr. + */ + mutex_unlock(&dev->struct_mutex); + unwritten = copy_from_user(vaddr, user_data, args->size); + mutex_lock(&dev->struct_mutex); + if (unwritten) + return -EFAULT; + } drm_agp_chipset_flush(dev); return 0; |