MIPS: Get rid of branches to .subsections.

It was a nice optimization - on paper at least.  In practice it results in
branches that may exceed the maximum legal range for a branch.  We can
fight that problem with -ffunction-sections but -ffunction-sections again
is incompatible with -pg used by the function tracer.

By rewriting the loop around all simple LL/SC blocks to C we reduce the
amount of inline assembler and at the same time allow GCC to often fill
the branch delay slots with something sensible or whatever else clever
optimization it may have up in its sleeve.

With this optimization gone we also no longer need -ffunction-sections,
so drop it.

This optimization was originally introduced in 2.6.21, commit
5999eca25c1fd4b9b9aca7833b04d10fe4bc877d (linux-mips.org) rsp.
f65e4fa8e0c6022ad58dc88d1b11b12589ed7f9f (kernel.org).

Original fix for the issues which caused me to pull this optimization by
Paul Gortmaker <paul.gortmaker@windriver.com>.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Makefile

@@ -48,9 +48,6 @@ ifneq ($(SUBARCH),$(ARCH))
   endif
 endif
 
-ifndef CONFIG_FUNCTION_TRACER
-cflags-y := -ffunction-sections
-endif
 ifdef CONFIG_FUNCTION_GRAPH_TRACER
   ifndef KBUILD_MCOUNT_RA_ADDRESS
     ifeq ($(call cc-option-yn,-mmcount-ra-address), y)

arch/mips/include/asm/atomic.h

@@ -64,18 +64,16 @@ static __inline__ void atomic_add(int i, atomic_t * v)
 	} else if (kernel_uses_llsc) {
 		int temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	ll	%0, %1		# atomic_add		\n"
-		"	addu	%0, %2					\n"
-		"	sc	%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter));
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	ll	%0, %1		# atomic_add	\n"
+			"	addu	%0, %2				\n"
+			"	sc	%0, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter));
+		} while (unlikely(!temp));
 	} else {
 		unsigned long flags;
 
@@ -109,18 +107,16 @@ static __inline__ void atomic_sub(int i, atomic_t * v)
 	} else if (kernel_uses_llsc) {
 		int temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	ll	%0, %1		# atomic_sub		\n"
-		"	subu	%0, %2					\n"
-		"	sc	%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter));
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	ll	%0, %1		# atomic_sub	\n"
+			"	subu	%0, %2				\n"
+			"	sc	%0, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter));
+		} while (unlikely(!temp));
 	} else {
 		unsigned long flags;
 
@@ -156,20 +152,19 @@ static __inline__ int atomic_add_return(int i, atomic_t * v)
 	} else if (kernel_uses_llsc) {
 		int temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	ll	%1, %2		# atomic_add_return	\n"
-		"	addu	%0, %1, %3				\n"
-		"	sc	%0, %2					\n"
-		"	beqz	%0, 2f					\n"
-		"	addu	%0, %1, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	ll	%1, %2	# atomic_add_return	\n"
+			"	addu	%0, %1, %3			\n"
+			"	sc	%0, %2				\n"
+			"	.set	mips0				\n"
+			: "=&r" (result), "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter)
+			: "memory");
+		} while (unlikely(!result));
+
+		result = temp + i;
 	} else {
 		unsigned long flags;
 
@@ -205,23 +200,24 @@ static __inline__ int atomic_sub_return(int i, atomic_t * v)
 		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
 		: "Ir" (i), "m" (v->counter)
 		: "memory");
+
+		result = temp - i;
 	} else if (kernel_uses_llsc) {
 		int temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	ll	%1, %2		# atomic_sub_return	\n"
-		"	subu	%0, %1, %3				\n"
-		"	sc	%0, %2					\n"
-		"	beqz	%0, 2f					\n"
-		"	subu	%0, %1, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	ll	%1, %2	# atomic_sub_return	\n"
+			"	subu	%0, %1, %3			\n"
+			"	sc	%0, %2				\n"
+			"	.set	mips0				\n"
+			: "=&r" (result), "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter)
+			: "memory");
+		} while (unlikely(!result));
+
+		result = temp - i;
 	} else {
 		unsigned long flags;
 
@@ -279,12 +275,9 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v)
 		"	bltz	%0, 1f					\n"
 		"	sc	%0, %2					\n"
 		"	.set	noreorder				\n"
-		"	beqz	%0, 2f					\n"
+		"	beqz	%0, 1b					\n"
 		"	 subu	%0, %1, %3				\n"
 		"	.set	reorder					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
 		"1:							\n"
 		"	.set	mips0					\n"
 		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
@@ -443,18 +436,16 @@ static __inline__ void atomic64_add(long i, atomic64_t * v)
 	} else if (kernel_uses_llsc) {
 		long temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	lld	%0, %1		# atomic64_add		\n"
-		"	daddu	%0, %2					\n"
-		"	scd	%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter));
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	lld	%0, %1		# atomic64_add	\n"
+			"	daddu	%0, %2				\n"
+			"	scd	%0, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter));
+		} while (unlikely(!temp));
 	} else {
 		unsigned long flags;
 
@@ -488,18 +479,16 @@ static __inline__ void atomic64_sub(long i, atomic64_t * v)
 	} else if (kernel_uses_llsc) {
 		long temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	lld	%0, %1		# atomic64_sub		\n"
-		"	dsubu	%0, %2					\n"
-		"	scd	%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter));
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	lld	%0, %1		# atomic64_sub	\n"
+			"	dsubu	%0, %2				\n"
+			"	scd	%0, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter));
+		} while (unlikely(!temp));
 	} else {
 		unsigned long flags;
 
@@ -535,20 +524,19 @@ static __inline__ long atomic64_add_return(long i, atomic64_t * v)
 	} else if (kernel_uses_llsc) {
 		long temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	lld	%1, %2		# atomic64_add_return	\n"
-		"	daddu	%0, %1, %3				\n"
-		"	scd	%0, %2					\n"
-		"	beqz	%0, 2f					\n"
-		"	daddu	%0, %1, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	lld	%1, %2	# atomic64_add_return	\n"
+			"	daddu	%0, %1, %3			\n"
+			"	scd	%0, %2				\n"
+			"	.set	mips0				\n"
+			: "=&r" (result), "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter)
+			: "memory");
+		} while (unlikely(!result));
+
+		result = temp + i;
 	} else {
 		unsigned long flags;
 
@@ -587,20 +575,19 @@ static __inline__ long atomic64_sub_return(long i, atomic64_t * v)
 	} else if (kernel_uses_llsc) {
 		long temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	lld	%1, %2		# atomic64_sub_return	\n"
-		"	dsubu	%0, %1, %3				\n"
-		"	scd	%0, %2					\n"
-		"	beqz	%0, 2f					\n"
-		"	dsubu	%0, %1, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (result), "=&r" (temp), "=m" (v->counter)
-		: "Ir" (i), "m" (v->counter)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	lld	%1, %2	# atomic64_sub_return	\n"
+			"	dsubu	%0, %1, %3			\n"
+			"	scd	%0, %2				\n"
+			"	.set	mips0				\n"
+			: "=&r" (result), "=&r" (temp), "=m" (v->counter)
+			: "Ir" (i), "m" (v->counter)
+			: "memory");
+		} while (unlikely(!result));
+
+		result = temp - i;
 	} else {
 		unsigned long flags;
 
@@ -658,12 +645,9 @@ static __inline__ long atomic64_sub_if_positive(long i, atomic64_t * v)
 		"	bltz	%0, 1f					\n"
 		"	scd	%0, %2					\n"
 		"	.set	noreorder				\n"
-		"	beqz	%0, 2f					\n"
+		"	beqz	%0, 1b					\n"
 		"	 dsubu	%0, %1, %3				\n"
 		"	.set	reorder					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
 		"1:							\n"
 		"	.set	mips0					\n"
 		: "=&r" (result), "=&r" (temp), "=m" (v->counter)

arch/mips/include/asm/bitops.h

@@ -73,30 +73,26 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *addr)
 		: "ir" (1UL << bit), "m" (*m));
 #ifdef CONFIG_CPU_MIPSR2
 	} else if (kernel_uses_llsc && __builtin_constant_p(bit)) {
-		__asm__ __volatile__(
-		"1:	" __LL "%0, %1			# set_bit	\n"
-		"	" __INS "%0, %4, %2, 1				\n"
-		"	" __SC "%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		: "=&r" (temp), "=m" (*m)
-		: "ir" (bit), "m" (*m), "r" (~0));
+		do {
+			__asm__ __volatile__(
+			"	" __LL "%0, %1		# set_bit	\n"
+			"	" __INS "%0, %3, %2, 1			\n"
+			"	" __SC "%0, %1				\n"
+			: "=&r" (temp), "+m" (*m)
+			: "ir" (bit), "r" (~0));
+		} while (unlikely(!temp));
 #endif /* CONFIG_CPU_MIPSR2 */
 	} else if (kernel_uses_llsc) {
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	" __LL "%0, %1			# set_bit	\n"
-		"	or	%0, %2					\n"
-		"	" __SC	"%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (*m)
-		: "ir" (1UL << bit), "m" (*m));
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	" __LL "%0, %1		# set_bit	\n"
+			"	or	%0, %2				\n"
+			"	" __SC	"%0, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "+m" (*m)
+			: "ir" (1UL << bit));
+		} while (unlikely(!temp));
 	} else {
 		volatile unsigned long *a = addr;
 		unsigned long mask;
@@ -134,34 +130,30 @@ static inline void clear_bit(unsigned long nr, volatile unsigned long *addr)
 		"	" __SC "%0, %1					\n"
 		"	beqzl	%0, 1b					\n"
 		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (*m)
-		: "ir" (~(1UL << bit)), "m" (*m));
+		: "=&r" (temp), "+m" (*m)
+		: "ir" (~(1UL << bit)));
 #ifdef CONFIG_CPU_MIPSR2
 	} else if (kernel_uses_llsc && __builtin_constant_p(bit)) {
-		__asm__ __volatile__(
-		"1:	" __LL "%0, %1			# clear_bit	\n"
-		"	" __INS "%0, $0, %2, 1				\n"
-		"	" __SC "%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		: "=&r" (temp), "=m" (*m)
-		: "ir" (bit), "m" (*m));
+		do {
+			__asm__ __volatile__(
+			"	" __LL "%0, %1		# clear_bit	\n"
+			"	" __INS "%0, $0, %2, 1			\n"
+			"	" __SC "%0, %1				\n"
+			: "=&r" (temp), "+m" (*m)
+			: "ir" (bit));
+		} while (unlikely(!temp));
 #endif /* CONFIG_CPU_MIPSR2 */
 	} else if (kernel_uses_llsc) {
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	" __LL "%0, %1			# clear_bit	\n"
-		"	and	%0, %2					\n"
-		"	" __SC "%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (*m)
-		: "ir" (~(1UL << bit)), "m" (*m));
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	" __LL "%0, %1		# clear_bit	\n"
+			"	and	%0, %2				\n"
+			"	" __SC "%0, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "+m" (*m)
+			: "ir" (~(1UL << bit)));
+		} while (unlikely(!temp));
 	} else {
 		volatile unsigned long *a = addr;
 		unsigned long mask;
@@ -213,24 +205,22 @@ static inline void change_bit(unsigned long nr, volatile unsigned long *addr)
 		"	" __SC	"%0, %1				\n"
 		"	beqzl	%0, 1b				\n"
 		"	.set	mips0				\n"
-		: "=&r" (temp), "=m" (*m)
-		: "ir" (1UL << bit), "m" (*m));
+		: "=&r" (temp), "+m" (*m)
+		: "ir" (1UL << bit));
 	} else if (kernel_uses_llsc) {
 		unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG);
 		unsigned long temp;
 
-		__asm__ __volatile__(
-		"	.set	mips3				\n"
-		"1:	" __LL "%0, %1		# change_bit	\n"
-		"	xor	%0, %2				\n"
-		"	" __SC	"%0, %1				\n"
-		"	beqz	%0, 2f				\n"
-		"	.subsection 2				\n"
-		"2:	b	1b				\n"
-		"	.previous				\n"
-		"	.set	mips0				\n"
-		: "=&r" (temp), "=m" (*m)
-		: "ir" (1UL << bit), "m" (*m));
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	" __LL "%0, %1		# change_bit	\n"
+			"	xor	%0, %2				\n"
+			"	" __SC	"%0, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "+m" (*m)
+			: "ir" (1UL << bit));
+		} while (unlikely(!temp));
 	} else {
 		volatile unsigned long *a = addr;
 		unsigned long mask;
@@ -272,30 +262,26 @@ static inline int test_and_set_bit(unsigned long nr,
 		"	beqzl	%2, 1b					\n"
 		"	and	%2, %0, %3				\n"
 		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
+		: "=&r" (temp), "+m" (*m), "=&r" (res)
+		: "r" (1UL << bit)
 		: "memory");
 	} else if (kernel_uses_llsc) {
 		unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG);
 		unsigned long temp;
 
-		__asm__ __volatile__(
-		"	.set	push					\n"
-		"	.set	noreorder				\n"
-		"	.set	mips3					\n"
-		"1:	" __LL "%0, %1		# test_and_set_bit	\n"
-		"	or	%2, %0, %3				\n"
-		"	" __SC	"%2, %1					\n"
-		"	beqz	%2, 2f					\n"
-		"	 and	%2, %0, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	 nop						\n"
-		"	.previous					\n"
-		"	.set	pop					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	" __LL "%0, %1	# test_and_set_bit	\n"
+			"	or	%2, %0, %3			\n"
+			"	" __SC	"%2, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "+m" (*m), "=&r" (res)
+			: "r" (1UL << bit)
+			: "memory");
+		} while (unlikely(!res));
+
+		res = temp & (1UL << bit);
 	} else {
 		volatile unsigned long *a = addr;
 		unsigned long mask;
@@ -340,30 +326,26 @@ static inline int test_and_set_bit_lock(unsigned long nr,
 		"	beqzl	%2, 1b					\n"
 		"	and	%2, %0, %3				\n"
 		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
+		: "=&r" (temp), "+m" (*m), "=&r" (res)
+		: "r" (1UL << bit)
 		: "memory");
 	} else if (kernel_uses_llsc) {
 		unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG);
 		unsigned long temp;
 
-		__asm__ __volatile__(
-		"	.set	push					\n"
-		"	.set	noreorder				\n"
-		"	.set	mips3					\n"
-		"1:	" __LL "%0, %1		# test_and_set_bit	\n"
-		"	or	%2, %0, %3				\n"
-		"	" __SC	"%2, %1					\n"
-		"	beqz	%2, 2f					\n"
-		"	 and	%2, %0, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	 nop						\n"
-		"	.previous					\n"
-		"	.set	pop					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	" __LL "%0, %1	# test_and_set_bit	\n"
+			"	or	%2, %0, %3			\n"
+			"	" __SC	"%2, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "+m" (*m), "=&r" (res)
+			: "r" (1UL << bit)
+			: "memory");
+		} while (unlikely(!res));
+
+		res = temp & (1UL << bit);
 	} else {
 		volatile unsigned long *a = addr;
 		unsigned long mask;
@@ -410,49 +392,43 @@ static inline int test_and_clear_bit(unsigned long nr,
 		"	beqzl	%2, 1b					\n"
 		"	and	%2, %0, %3				\n"
 		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
+		: "=&r" (temp), "+m" (*m), "=&r" (res)
+		: "r" (1UL << bit)
 		: "memory");
 #ifdef CONFIG_CPU_MIPSR2
 	} else if (kernel_uses_llsc && __builtin_constant_p(nr)) {
 		unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG);
 		unsigned long temp;
 
-		__asm__ __volatile__(
-		"1:	" __LL	"%0, %1		# test_and_clear_bit	\n"
-		"	" __EXT "%2, %0, %3, 1				\n"
-		"	" __INS	"%0, $0, %3, 1				\n"
-		"	" __SC 	"%0, %1					\n"
-		"	beqz	%0, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "ir" (bit), "m" (*m)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	" __LL	"%0, %1	# test_and_clear_bit	\n"
+			"	" __EXT "%2, %0, %3, 1			\n"
+			"	" __INS	"%0, $0, %3, 1			\n"
+			"	" __SC 	"%0, %1				\n"
+			: "=&r" (temp), "+m" (*m), "=&r" (res)
+			: "ir" (bit)
+			: "memory");
+		} while (unlikely(!temp));
 #endif
 	} else if (kernel_uses_llsc) {
 		unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG);
 		unsigned long temp;
 
-		__asm__ __volatile__(
-		"	.set	push					\n"
-		"	.set	noreorder				\n"
-		"	.set	mips3					\n"
-		"1:	" __LL	"%0, %1		# test_and_clear_bit	\n"
-		"	or	%2, %0, %3				\n"
-		"	xor	%2, %3					\n"
-		"	" __SC 	"%2, %1					\n"
-		"	beqz	%2, 2f					\n"
-		"	 and	%2, %0, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	 nop						\n"
-		"	.previous					\n"
-		"	.set	pop					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	" __LL	"%0, %1	# test_and_clear_bit	\n"
+			"	or	%2, %0, %3			\n"
+			"	xor	%2, %3				\n"
+			"	" __SC 	"%2, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "+m" (*m), "=&r" (res)
+			: "r" (1UL << bit)
+			: "memory");
+		} while (unlikely(!res));
+
+		res = temp & (1UL << bit);
 	} else {
 		volatile unsigned long *a = addr;
 		unsigned long mask;
@@ -499,30 +475,26 @@ static inline int test_and_change_bit(unsigned long nr,
 		"	beqzl	%2, 1b					\n"
 		"	and	%2, %0, %3				\n"
 		"	.set	mips0					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
+		: "=&r" (temp), "+m" (*m), "=&r" (res)
+		: "r" (1UL << bit)
 		: "memory");
 	} else if (kernel_uses_llsc) {
 		unsigned long *m = ((unsigned long *) addr) + (nr >> SZLONG_LOG);
 		unsigned long temp;
 
-		__asm__ __volatile__(
-		"	.set	push					\n"
-		"	.set	noreorder				\n"
-		"	.set	mips3					\n"
-		"1:	" __LL	"%0, %1		# test_and_change_bit	\n"
-		"	xor	%2, %0, %3				\n"
-		"	" __SC	"\t%2, %1				\n"
-		"	beqz	%2, 2f					\n"
-		"	 and	%2, %0, %3				\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	 nop						\n"
-		"	.previous					\n"
-		"	.set	pop					\n"
-		: "=&r" (temp), "=m" (*m), "=&r" (res)
-		: "r" (1UL << bit), "m" (*m)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	" __LL	"%0, %1	# test_and_change_bit	\n"
+			"	xor	%2, %0, %3			\n"
+			"	" __SC	"\t%2, %1			\n"
+			"	.set	mips0				\n"
+			: "=&r" (temp), "+m" (*m), "=&r" (res)
+			: "r" (1UL << bit)
+			: "memory");
+		} while (unlikely(!res));
+
+		res = temp & (1UL << bit);
 	} else {
 		volatile unsigned long *a = addr;
 		unsigned long mask;

arch/mips/include/asm/cmpxchg.h

@@ -44,12 +44,9 @@
 		"	move	$1, %z4				\n"	\
 		"	.set	mips3				\n"	\
 		"	" st "	$1, %1				\n"	\
-		"	beqz	$1, 3f				\n"	\
-		"2:						\n"	\
-		"	.subsection 2				\n"	\
-		"3:	b	1b				\n"	\
-		"	.previous				\n"	\
+		"	beqz	$1, 1b				\n"	\
 		"	.set	pop				\n"	\
+		"2:						\n"	\
 		: "=&r" (__ret), "=R" (*m)				\
 		: "R" (*m), "Jr" (old), "Jr" (new)			\
 		: "memory");						\

arch/mips/include/asm/system.h

@@ -115,21 +115,19 @@ static inline unsigned long __xchg_u32(volatile int * m, unsigned int val)
 	} else if (kernel_uses_llsc) {
 		unsigned long dummy;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	ll	%0, %3			# xchg_u32	\n"
-		"	.set	mips0					\n"
-		"	move	%2, %z4					\n"
-		"	.set	mips3					\n"
-		"	sc	%2, %1					\n"
-		"	beqz	%2, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (retval), "=m" (*m), "=&r" (dummy)
-		: "R" (*m), "Jr" (val)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	ll	%0, %3		# xchg_u32	\n"
+			"	.set	mips0				\n"
+			"	move	%2, %z4				\n"
+			"	.set	mips3				\n"
+			"	sc	%2, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (retval), "=m" (*m), "=&r" (dummy)
+			: "R" (*m), "Jr" (val)
+			: "memory");
+		} while (unlikely(!dummy));
 	} else {
 		unsigned long flags;
 
@@ -167,19 +165,17 @@ static inline __u64 __xchg_u64(volatile __u64 * m, __u64 val)
 	} else if (kernel_uses_llsc) {
 		unsigned long dummy;
 
-		__asm__ __volatile__(
-		"	.set	mips3					\n"
-		"1:	lld	%0, %3			# xchg_u64	\n"
-		"	move	%2, %z4					\n"
-		"	scd	%2, %1					\n"
-		"	beqz	%2, 2f					\n"
-		"	.subsection 2					\n"
-		"2:	b	1b					\n"
-		"	.previous					\n"
-		"	.set	mips0					\n"
-		: "=&r" (retval), "=m" (*m), "=&r" (dummy)
-		: "R" (*m), "Jr" (val)
-		: "memory");
+		do {
+			__asm__ __volatile__(
+			"	.set	mips3				\n"
+			"	lld	%0, %3		# xchg_u64	\n"
+			"	move	%2, %z4				\n"
+			"	scd	%2, %1				\n"
+			"	.set	mips0				\n"
+			: "=&r" (retval), "=m" (*m), "=&r" (dummy)
+			: "R" (*m), "Jr" (val)
+			: "memory");
+		} while (unlikely(!dummy));
 	} else {
 		unsigned long flags;