drm/i915: Nuke struct_mutex from context_setparam

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.

v2: Separate user_flags from internal flags to reduce chance of
interference; and use locked bit ops for user updates.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180911132206.23032-1-chris@chris-wilson.co.uk

1 files changed, 19 insertions, 14 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index e09673ca731d..08165f6a0a84 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -117,15 +117,20 @@ struct i915_gem_context {
 	struct rcu_head rcu;
 
 	/**
+	 * @user_flags: small set of booleans controlled by the user
+	 */
+	unsigned long user_flags;
+#define UCONTEXT_NO_ZEROMAP		0
+#define UCONTEXT_NO_ERROR_CAPTURE	1
+#define UCONTEXT_BANNABLE		2
+
+	/**
 	 * @flags: small set of booleans
 	 */
 	unsigned long flags;
-#define CONTEXT_NO_ZEROMAP		BIT(0)
-#define CONTEXT_NO_ERROR_CAPTURE	1
-#define CONTEXT_CLOSED			2
-#define CONTEXT_BANNABLE		3
-#define CONTEXT_BANNED			4
-#define CONTEXT_FORCE_SINGLE_SUBMISSION	5
+#define CONTEXT_BANNED			0
+#define CONTEXT_CLOSED			1
+#define CONTEXT_FORCE_SINGLE_SUBMISSION	2
 
 	/**
 	 * @hw_id: - unique identifier for the context
@@ -209,37 +214,37 @@ static inline bool i915_gem_context_is_closed(const struct i915_gem_context *ctx
 static inline void i915_gem_context_set_closed(struct i915_gem_context *ctx)
 {
 	GEM_BUG_ON(i915_gem_context_is_closed(ctx));
-	__set_bit(CONTEXT_CLOSED, &ctx->flags);
+	set_bit(CONTEXT_CLOSED, &ctx->flags);
 }
 
 static inline bool i915_gem_context_no_error_capture(const struct i915_gem_context *ctx)
 {
-	return test_bit(CONTEXT_NO_ERROR_CAPTURE, &ctx->flags);
+	return test_bit(UCONTEXT_NO_ERROR_CAPTURE, &ctx->user_flags);
 }
 
 static inline void i915_gem_context_set_no_error_capture(struct i915_gem_context *ctx)
 {
-	__set_bit(CONTEXT_NO_ERROR_CAPTURE, &ctx->flags);
+	set_bit(UCONTEXT_NO_ERROR_CAPTURE, &ctx->user_flags);
 }
 
 static inline void i915_gem_context_clear_no_error_capture(struct i915_gem_context *ctx)
 {
-	__clear_bit(CONTEXT_NO_ERROR_CAPTURE, &ctx->flags);
+	clear_bit(UCONTEXT_NO_ERROR_CAPTURE, &ctx->user_flags);
 }
 
 static inline bool i915_gem_context_is_bannable(const struct i915_gem_context *ctx)
 {
-	return test_bit(CONTEXT_BANNABLE, &ctx->flags);
+	return test_bit(UCONTEXT_BANNABLE, &ctx->user_flags);
 }
 
 static inline void i915_gem_context_set_bannable(struct i915_gem_context *ctx)
 {
-	__set_bit(CONTEXT_BANNABLE, &ctx->flags);
+	set_bit(UCONTEXT_BANNABLE, &ctx->user_flags);
 }
 
 static inline void i915_gem_context_clear_bannable(struct i915_gem_context *ctx)
 {
-	__clear_bit(CONTEXT_BANNABLE, &ctx->flags);
+	clear_bit(UCONTEXT_BANNABLE, &ctx->user_flags);
 }
 
 static inline bool i915_gem_context_is_banned(const struct i915_gem_context *ctx)
@@ -249,7 +254,7 @@ static inline bool i915_gem_context_is_banned(const struct i915_gem_context *ctx
 
 static inline void i915_gem_context_set_banned(struct i915_gem_context *ctx)
 {
-	__set_bit(CONTEXT_BANNED, &ctx->flags);
+	set_bit(CONTEXT_BANNED, &ctx->flags);
 }
 
 static inline bool i915_gem_context_force_single_submission(const struct i915_gem_context *ctx)