svn commit: r329524 - head/sys/compat/linuxkpi/common/include/asm

[Hans Petter Selasky]

Author: hselasky
Date: Sun Feb 18 18:46:56 2018
New Revision: 329524
URL: https://svnweb.freebsd.org/changeset/base/329524

Log:
  Optimise xchg() to use atomic_swap_32() and atomic_swap_64().
  
  Suggested by:	kib@
  MFC after:	1 week
  Sponsored by:	Mellanox Technologies

Modified:
  head/sys/compat/linuxkpi/common/include/asm/atomic.h

Modified: head/sys/compat/linuxkpi/common/include/asm/atomic.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/asm/atomic.h	Sun Feb 18 17:37:23 2018	(r329523)
+++ head/sys/compat/linuxkpi/common/include/asm/atomic.h	Sun Feb 18 18:46:56 2018	(r329524)
@@ -205,31 +205,31 @@ atomic_cmpxchg(atomic_t *v, int old, int new)
 		u16 u16[0];						\
 		u32 u32[0];						\
 		u64 u64[0];						\
-	} __ret = { .val = READ_ONCE(*ptr) }, __new = { .val = (new) };	\
+	} __ret, __new = { .val = (new) };				\
 									\
 	CTASSERT(sizeof(__ret.val) == 1 || sizeof(__ret.val) == 2 ||	\
 	    sizeof(__ret.val) == 4 || sizeof(__ret.val) == 8);		\
 									\
 	switch (sizeof(__ret.val)) {					\
 	case 1:								\
+		__ret.val = READ_ONCE(*ptr);				\
 		while (!atomic_fcmpset_8((volatile u8 *)(ptr),		\
 	            __ret.u8, __new.u8[0]))				\
 			;						\
 		break;							\
 	case 2:								\
+		__ret.val = READ_ONCE(*ptr);				\
 		while (!atomic_fcmpset_16((volatile u16 *)(ptr),	\
 	            __ret.u16, __new.u16[0]))				\
 			;						\
 		break;							\
 	case 4:								\
-		while (!atomic_fcmpset_32((volatile u32 *)(ptr),	\
-	            __ret.u32, __new.u32[0]))				\
-			;						\
+		__ret.u32[0] = atomic_swap_32((volatile u32 *)(ptr),	\
+		    __new.u32[0]);					\
 		break;							\
 	case 8:								\
-		while (!atomic_fcmpset_64((volatile u64 *)(ptr),	\
-	            __ret.u64, __new.u64[0]))				\
-			;						\
+		__ret.u64[0] = atomic_swap_64((volatile u64 *)(ptr),	\
+		    __new.u64[0]);					\
 		break;							\
 	}								\
 	__ret.val;							\