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drm/i915: Reduce locking inside swfinish ioctl 

We only need to take the struct_mutex if the object is pinned to the
display engine and so requires checking for clflush. (The race with
userspace pinning the object to a framebuffer is irrelevant.)

v2: Use access once for compiler hints (or not as it is a bitfield)
v3: READ_ONCE, obj->pin_display is not a bitfield anymore
v4: Don't be creative with goto.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-14-git-send-email-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2016-08-05 10:14:19 +01:00
parent 3fdc13c7a3
commit c21724cc4d
1 changed files with 12 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
drivers/gpu/drm/i915/i915_gem.c
View File

@ -1518,26 +1518,23 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data,
{
struct drm_i915_gem_sw_finish *args = data;
struct drm_i915_gem_object *obj;
int ret = 0;
ret = i915_mutex_lock_interruptible(dev);
if (ret)
return ret;
int err = 0;
obj = i915_gem_object_lookup(file, args->handle);
if (!obj) {
ret = -ENOENT;
goto unlock;
}
if (!obj)
return -ENOENT;
/* Pinned buffers may be scanout, so flush the cache */
if (obj->pin_display)
i915_gem_object_flush_cpu_write_domain(obj);
if (READ_ONCE(obj->pin_display)) {
err = i915_mutex_lock_interruptible(dev);
if (!err) {
i915_gem_object_flush_cpu_write_domain(obj);
mutex_unlock(&dev->struct_mutex);
}
}
i915_gem_object_put(obj);
unlock:
mutex_unlock(&dev->struct_mutex);
return ret;
i915_gem_object_put_unlocked(obj);
return err;
}
/**