[PATCH] drm/i915: Ditch the i915_gem_ww_ctx loop member

[Thomas Hellström]

It's only used by the for_i915_gem_ww() macro and we can use
the (typically) on-stack _err variable in its place.

While initially setting the _err variable to -EDEADLK to enter the
loop, we clear it before actually entering using fetch_and_zero() to
avoid empty loops or code not setting the _err variable running forever.

Suggested-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_ww.h | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h b/drivers/gpu/drm/i915/i915_gem_ww.h
index f6b1a796667b..98348b1e6182 100644
--- a/drivers/gpu/drm/i915/i915_gem_ww.h
+++ b/drivers/gpu/drm/i915/i915_gem_ww.h
@@ -7,12 +7,13 @@
 
 #include <drm/drm_drv.h>
 
+#include "i915_utils.h"
+
 struct i915_gem_ww_ctx {
 	struct ww_acquire_ctx ctx;
 	struct list_head obj_list;
 	struct drm_i915_gem_object *contended;
-	unsigned short intr;
-	unsigned short loop;
+	bool intr;
 };
 
 void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
@@ -23,28 +24,20 @@ void i915_gem_ww_unlock_single(struct drm_i915_gem_object *obj);
 /* Internal functions used by the inlines! Don't use. */
 static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
 {
-	ww->loop = 0;
 	if (err == -EDEADLK) {
 		err = i915_gem_ww_ctx_backoff(ww);
 		if (!err)
-			ww->loop = 1;
+			err = -EDEADLK;
 	}
 
-	if (!ww->loop)
+	if (err != -EDEADLK)
 		i915_gem_ww_ctx_fini(ww);
 
 	return err;
 }
 
-static inline void
-__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr)
-{
-	i915_gem_ww_ctx_init(ww, intr);
-	ww->loop = 1;
-}
-
-#define for_i915_gem_ww(_ww, _err, _intr)			\
-	for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop;	\
+#define for_i915_gem_ww(_ww, _err, _intr)			  \
+	for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \
+	     fetch_and_zero(&_err) == -EDEADLK;			  \
 	     _err = __i915_gem_ww_fini(_ww, _err))
-
 #endif
-- 
2.31.1