On 25/01/2021 14:01, Chris Wilson wrote:
Wrap cmpxchg64 with a try_cmpxchg()-esque helper. Hiding the old-value
dance in the helper allows for cleaner code.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_utils.h | 32 +++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
index abd4dcd9f79c..95ead6bb1ba6 100644
--- a/drivers/gpu/drm/i915/i915_utils.h
+++ b/drivers/gpu/drm/i915/i915_utils.h
@@ -461,4 +461,36 @@ static inline bool timer_expired(const struct timer_list *t)
*/
#define IS_ACTIVE(config) ((config) != 0)
+#ifndef try_cmpxchg64
+#if IS_ENABLED(CONFIG_64BIT)
+#define try_cmpxchg64(_ptr, _pold, _new) try_cmpxchg(_ptr, _pold, _new)
+#else
+#define try_cmpxchg64(_ptr, _pold, _new) \
+({ \
+ __typeof__(_ptr) _old = (__typeof__(_ptr))(_pold); \
+ __typeof__(*(_ptr)) __old = *_old; \
+ __typeof__(*(_ptr)) __cur = cmpxchg64(_ptr, __old, _new); \
+ bool success = __cur == __old; \
+ if (unlikely(!success)) \
+ *_old = __cur; \
+ likely(success); \
+})
+#endif
+#endif
+
+#ifndef xchg64
+#if IS_ENABLED(CONFIG_64BIT)
+#define xchg64(_ptr, _new) xchg(_ptr, _new)
+#else
+#define xchg64(_ptr, _new) \
+({ \
+ __typeof__(_ptr) __ptr = (_ptr); \
+ __typeof__(*(_ptr)) __old = *__ptr; \
+ while (!try_cmpxchg64(__ptr, &__old, (_new))) \
+ ; \
+ __old; \
+})
+#endif
+#endif
+
#endif /* !__I915_UTILS_H */
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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