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MIPS: bitops: Implement test_and_set_bit() in terms of _lock variant 

The only difference between test_and_set_bit() & test_and_set_bit_lock()
is memory ordering barrier semantics - the former provides a full
barrier whilst the latter only provides acquire semantics.

We can therefore implement test_and_set_bit() in terms of
test_and_set_bit_lock() with the addition of the extra memory barrier.
Do this in order to avoid duplicating logic.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: linux-kernel@vger.kernel.org
This commit is contained in:
Paul Burton 2019-10-01 21:53:30 +00:00
parent 27aab27259
commit 6bbe043bd3
No known key found for this signature in database
GPG Key ID: 3EA79FACB57500DD
2 changed files with 17 additions and 83 deletions
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74
arch/mips/include/asm/bitops.h
View File

@ -31,8 +31,6 @@
void __mips_set_bit(unsigned long nr, volatile unsigned long *addr); void __mips_set_bit(unsigned long nr, volatile unsigned long *addr);
void __mips_clear_bit(unsigned long nr, volatile unsigned long *addr); void __mips_clear_bit(unsigned long nr, volatile unsigned long *addr);
void __mips_change_bit(unsigned long nr, volatile unsigned long *addr); void __mips_change_bit(unsigned long nr, volatile unsigned long *addr);
int __mips_test_and_set_bit(unsigned long nr,
volatile unsigned long *addr);
int __mips_test_and_set_bit_lock(unsigned long nr, int __mips_test_and_set_bit_lock(unsigned long nr,
volatile unsigned long *addr); volatile unsigned long *addr);
int __mips_test_and_clear_bit(unsigned long nr, int __mips_test_and_clear_bit(unsigned long nr,
@ -235,61 +233,6 @@ static inline void change_bit(unsigned long nr, volatile unsigned long *addr)
} while (unlikely(!temp)); } while (unlikely(!temp));
} }
/*
* test_and_set_bit - Set a bit and return its old value
* @nr: Bit to set
* @addr: Address to count from
*
* This operation is atomic and cannot be reordered.
* It also implies a memory barrier.
*/
static inline int test_and_set_bit(unsigned long nr,
volatile unsigned long *addr)
{
unsigned long *m = ((unsigned long *)addr) + (nr >> SZLONG_LOG);
int bit = nr & SZLONG_MASK;
unsigned long res, temp;
smp_mb__before_llsc();
if (!kernel_uses_llsc) {
res = __mips_test_and_set_bit(nr, addr);
} else if (R10000_LLSC_WAR) {
__asm__ __volatile__(
" .set push \n"
" .set arch=r4000 \n"
"1: " __LL "%0, %1 # test_and_set_bit \n"
" or %2, %0, %3 \n"
" " __SC "%2, %1 \n"
" beqzl %2, 1b \n"
" and %2, %0, %3 \n"
" .set pop \n"
: "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res)
: "r" (1UL << bit)
: __LLSC_CLOBBER);
} else {
loongson_llsc_mb();
do {
__asm__ __volatile__(
" .set push \n"
" .set "MIPS_ISA_ARCH_LEVEL" \n"
" " __LL "%0, %1 # test_and_set_bit \n"
" or %2, %0, %3 \n"
" " __SC "%2, %1 \n"
" .set pop \n"
: "=&r" (temp), "+" GCC_OFF_SMALL_ASM() (*m), "=&r" (res)
: "r" (1UL << bit)
: __LLSC_CLOBBER);
} while (unlikely(!res));
res = temp & (1UL << bit);
}
smp_llsc_mb();
return res != 0;
}
/* /*
* test_and_set_bit_lock - Set a bit and return its old value * test_and_set_bit_lock - Set a bit and return its old value
* @nr: Bit to set * @nr: Bit to set
@ -321,6 +264,7 @@ static inline int test_and_set_bit_lock(unsigned long nr,
: "r" (1UL << bit) : "r" (1UL << bit)
: __LLSC_CLOBBER); : __LLSC_CLOBBER);
} else { } else {
loongson_llsc_mb();
do { do {
__asm__ __volatile__( __asm__ __volatile__(
" .set push \n" " .set push \n"
@ -341,6 +285,22 @@ static inline int test_and_set_bit_lock(unsigned long nr,
return res != 0; return res != 0;
} }
/*
* test_and_set_bit - Set a bit and return its old value
* @nr: Bit to set
* @addr: Address to count from
*
* This operation is atomic and cannot be reordered.
* It also implies a memory barrier.
*/
static inline int test_and_set_bit(unsigned long nr,
volatile unsigned long *addr)
{
smp_mb__before_llsc();
return test_and_set_bit_lock(nr, addr);
}
/* /*
* test_and_clear_bit - Clear a bit and return its old value * test_and_clear_bit - Clear a bit and return its old value
* @nr: Bit to clear * @nr: Bit to clear

26
arch/mips/lib/bitops.c
View File

@ -77,32 +77,6 @@ void __mips_change_bit(unsigned long nr, volatile unsigned long *addr)
EXPORT_SYMBOL(__mips_change_bit); EXPORT_SYMBOL(__mips_change_bit);
/**
* __mips_test_and_set_bit - Set a bit and return its old value. This is
* called by test_and_set_bit() if it cannot find a faster solution.
* @nr: Bit to set
* @addr: Address to count from
*/
int __mips_test_and_set_bit(unsigned long nr,
volatile unsigned long *addr)
{
unsigned long *a = (unsigned long *)addr;
unsigned bit = nr & SZLONG_MASK;
unsigned long mask;
unsigned long flags;
int res;
a += nr >> SZLONG_LOG;
mask = 1UL << bit;
raw_local_irq_save(flags);
res = (mask & *a) != 0;
*a |= mask;
raw_local_irq_restore(flags);
return res;
}
EXPORT_SYMBOL(__mips_test_and_set_bit);
/** /**
* __mips_test_and_set_bit_lock - Set a bit and return its old value. This is * __mips_test_and_set_bit_lock - Set a bit and return its old value. This is
* called by test_and_set_bit_lock() if it cannot find a faster solution. * called by test_and_set_bit_lock() if it cannot find a faster solution.