Commit 30c23f29 authored by Miguel Bernal Marin's avatar Miguel Bernal Marin Committed by Ingo Molnar
Browse files

locking/x86: Use named operands in rwsem.h 



Since GCC version 3.1 it is possible to specify input and output
operands using symbolic names, which can be referenced within the
assembler code.

Converting to named operands makes it easier to understand and maintain
the code in the future.

Update operands in asm/rwsem.h accordingly.

Signed-off-by: default avatarMiguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170925230349.18834-1-miguel.bernal.marin@linux.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9cd6681c

arch/x86/include/asm/rwsem.h

+27 −26
Original line number Diff line number Diff line
@@ -63,14 +63,14 @@ 
static inline void __down_read(struct rw_semaphore *sem)

{

	asm volatile("# beginning down_read\n\t"

		     LOCK_PREFIX _ASM_INC "(%1)\n\t"

		     LOCK_PREFIX _ASM_INC "(%[sem])\n\t"

		     /* adds 0x00000001 */

		     "  jns        1f\n"

		     "  call call_rwsem_down_read_failed\n"

		     "1:\n\t"

		     "# ending down_read\n\t"

		     : "+m" (sem->count)

		     : "a" (sem)

		     : [sem] "a" (sem)

		     : "memory", "cc");

}
@@ -81,17 +81,18 @@ static inline bool __down_read_trylock(struct rw_semaphore *sem) 
{

	long result, tmp;

	asm volatile("# beginning __down_read_trylock\n\t"

		     "  mov          %0,%1\n\t"

		     "  mov          %[count],%[result]\n\t"

		     "1:\n\t"

		     "  mov          %1,%2\n\t"

		     "  add          %3,%2\n\t"

		     "  mov          %[result],%[tmp]\n\t"

		     "  add          %[inc],%[tmp]\n\t"

		     "  jle	     2f\n\t"

		     LOCK_PREFIX "  cmpxchg  %2,%0\n\t"

		     LOCK_PREFIX "  cmpxchg  %[tmp],%[count]\n\t"

		     "  jnz	     1b\n\t"

		     "2:\n\t"

		     "# ending __down_read_trylock\n\t"

		     : "+m" (sem->count), "=&a" (result), "=&r" (tmp)

		     : "i" (RWSEM_ACTIVE_READ_BIAS)

		     : [count] "+m" (sem->count), [result] "=&a" (result),

		       [tmp] "=&r" (tmp)

		     : [inc] "i" (RWSEM_ACTIVE_READ_BIAS)

		     : "memory", "cc");

	return result >= 0;

}
@@ -105,7 +106,7 @@ static inline bool __down_read_trylock(struct rw_semaphore *sem) 
	struct rw_semaphore* ret;			\

							\

	asm volatile("# beginning down_write\n\t"	\

		     LOCK_PREFIX "  xadd      %1,(%4)\n\t"	\

		     LOCK_PREFIX "  xadd      %[tmp],(%[sem])\n\t"	\

		     /* adds 0xffff0001, returns the old value */ \

		     "  test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \

		     /* was the active mask 0 before? */\
@@ -113,9 +114,9 @@ static inline bool __down_read_trylock(struct rw_semaphore *sem) 
		     "  call " slow_path "\n"		\

		     "1:\n"				\

		     "# ending down_write"		\

		     : "+m" (sem->count), "=d" (tmp),	\

		     : "+m" (sem->count), [tmp] "=d" (tmp),	\

		       "=a" (ret), ASM_CALL_CONSTRAINT	\

		     : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \

		     : [sem] "a" (sem), "[tmp]" (RWSEM_ACTIVE_WRITE_BIAS) \

		     : "memory", "cc");			\

	ret;						\

})
@@ -141,21 +142,21 @@ static inline bool __down_write_trylock(struct rw_semaphore *sem) 
	bool result;

	long tmp0, tmp1;

	asm volatile("# beginning __down_write_trylock\n\t"

		     "  mov          %0,%1\n\t"

		     "  mov          %[count],%[tmp0]\n\t"

		     "1:\n\t"

		     "  test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t"

		     /* was the active mask 0 before? */

		     "  jnz          2f\n\t"

		     "  mov          %1,%2\n\t"

		     "  add          %4,%2\n\t"

		     LOCK_PREFIX "  cmpxchg  %2,%0\n\t"

		     "  mov          %[tmp0],%[tmp1]\n\t"

		     "  add          %[inc],%[tmp1]\n\t"

		     LOCK_PREFIX "  cmpxchg  %[tmp1],%[count]\n\t"

		     "  jnz	     1b\n\t"

		     "2:\n\t"

		     CC_SET(e)

		     "# ending __down_write_trylock\n\t"

		     : "+m" (sem->count), "=&a" (tmp0), "=&r" (tmp1),

		       CC_OUT(e) (result)

		     : "er" (RWSEM_ACTIVE_WRITE_BIAS)

		     : [count] "+m" (sem->count), [tmp0] "=&a" (tmp0),

		       [tmp1] "=&r" (tmp1), CC_OUT(e) (result)

		     : [inc] "er" (RWSEM_ACTIVE_WRITE_BIAS)

		     : "memory");

	return result;

}
@@ -167,14 +168,14 @@ static inline void __up_read(struct rw_semaphore *sem) 
{

	long tmp;

	asm volatile("# beginning __up_read\n\t"

		     LOCK_PREFIX "  xadd      %1,(%2)\n\t"

		     LOCK_PREFIX "  xadd      %[tmp],(%[sem])\n\t"

		     /* subtracts 1, returns the old value */

		     "  jns        1f\n\t"

		     "  call call_rwsem_wake\n" /* expects old value in %edx */

		     "1:\n"

		     "# ending __up_read\n"

		     : "+m" (sem->count), "=d" (tmp)

		     : "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS)

		     : "+m" (sem->count), [tmp] "=d" (tmp)

		     : [sem] "a" (sem), "[tmp]" (-RWSEM_ACTIVE_READ_BIAS)

		     : "memory", "cc");

}
@@ -185,14 +186,14 @@ static inline void __up_write(struct rw_semaphore *sem) 
{

	long tmp;

	asm volatile("# beginning __up_write\n\t"

		     LOCK_PREFIX "  xadd      %1,(%2)\n\t"

		     LOCK_PREFIX "  xadd      %[tmp],(%[sem])\n\t"

		     /* subtracts 0xffff0001, returns the old value */

		     "  jns        1f\n\t"

		     "  call call_rwsem_wake\n" /* expects old value in %edx */

		     "1:\n\t"

		     "# ending __up_write\n"

		     : "+m" (sem->count), "=d" (tmp)

		     : "a" (sem), "1" (-RWSEM_ACTIVE_WRITE_BIAS)

		     : "+m" (sem->count), [tmp] "=d" (tmp)

		     : [sem] "a" (sem), "[tmp]" (-RWSEM_ACTIVE_WRITE_BIAS)

		     : "memory", "cc");

}
@@ -202,7 +203,7 @@ static inline void __up_write(struct rw_semaphore *sem) 
static inline void __downgrade_write(struct rw_semaphore *sem)

{

	asm volatile("# beginning __downgrade_write\n\t"

		     LOCK_PREFIX _ASM_ADD "%2,(%1)\n\t"

		     LOCK_PREFIX _ASM_ADD "%[inc],(%[sem])\n\t"

		     /*

		      * transitions 0xZZZZ0001 -> 0xYYYY0001 (i386)

		      *     0xZZZZZZZZ00000001 -> 0xYYYYYYYY00000001 (x86_64)
@@ -212,7 +213,7 @@ static inline void __downgrade_write(struct rw_semaphore *sem) 
		     "1:\n\t"

		     "# ending __downgrade_write\n"

		     : "+m" (sem->count)

		     : "a" (sem), "er" (-RWSEM_WAITING_BIAS)

		     : [sem] "a" (sem), [inc] "er" (-RWSEM_WAITING_BIAS)

		     : "memory", "cc");

}

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