Userspace should be free to race against itself and shoot itself in
the foot if it so desires to adjust a parameter at the same time as
submitting a batch to that context. As such, the struct_mutex in context
setparam is only being used to serialise userspace against itself and
not for any protection of internal structs and so is superfluous.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c 
b/drivers/gpu/drm/i915/i915_gem_context.c
index 747b8170a15a..10fd742b591d 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -896,16 +896,12 @@ int i915_gem_context_setparam_ioctl(struct drm_device 
*dev, void *data,
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct drm_i915_gem_context_param *args = data;
        struct i915_gem_context *ctx;
-       int ret;
+       int ret = 0;
 
        ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
        if (!ctx)
                return -ENOENT;
 
-       ret = i915_mutex_lock_interruptible(dev);
-       if (ret)
-               goto out;
-
        switch (args->param) {
        case I915_CONTEXT_PARAM_BAN_PERIOD:
                ret = -EINVAL;
@@ -960,9 +956,7 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, 
void *data,
                ret = -EINVAL;
                break;
        }
-       mutex_unlock(&dev->struct_mutex);
 
-out:
        i915_gem_context_put(ctx);
        return ret;
 }
-- 
2.19.0.rc2

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