Messages in this thread Patch in this message | | | From | Satyam Sharma <> | Date | Mon, 23 Jul 2007 21:35:48 +0530 | Subject | [PATCH 4/8] i386: bitops: Kill volatile-casting of memory addresses |
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From: Satyam Sharma <ssatyam@cse.iitk.ac.in>
[4/8] i386: bitops: Kill volatile-casting of memory addresses
All the occurrences of "volatile" that are used to qualify access to the passed bit-string pointer/address must be removed, because "volatile" is crazy, doesn't really work anyway, has nothing to do with locking and atomicity, and is in general wholly unnecessary for these operations:
* In the case of the unlocked variants, we're not providing any guarantees whatsoever, so we want the caller to do any necessary locking surrounding the use of that function anyway.
* In case of the primitives where we *do* make locking/atomicity/reordering (three very different, but related, concepts) guarantees, we're doing that properly by using the lock instruction-prefix and "__asm__ __volatile__" anyway (and with "addr" always being constrained with "m" in the assembly, gcc doesn't bring it into a local register either).
So let's just kill the pointless use of volatile.
Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in> Cc: David Howells <dhowells@redhat.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au>
---
include/asm-i386/bitops.h | 60 +++++++++++++++++++++------------------------ 1 files changed, 28 insertions(+), 32 deletions(-)
diff --git a/include/asm-i386/bitops.h b/include/asm-i386/bitops.h index d623fd9..0f5634b 100644 --- a/include/asm-i386/bitops.h +++ b/include/asm-i386/bitops.h @@ -26,8 +26,6 @@ * on single-dword quantities. */ -#define ADDR (*(volatile long *) addr) - /** * set_bit - Atomically set a bit in memory * @nr: the bit to set @@ -38,11 +36,11 @@ * * See __set_bit() if you do not require the atomic guarantees. */ -static inline void set_bit(int nr, volatile unsigned long * addr) +static inline void set_bit(int nr, unsigned long *addr) { __asm__ __volatile__( LOCK_PREFIX "btsl %1,%0" - :"=m" (ADDR) + :"=m" (*addr) :"r" (nr)); } @@ -58,11 +56,11 @@ static inline void set_bit(int nr, volatile unsigned long * addr) * This is a fast and unlocked operation, and only suitable for callers * that already implement higher-level locking to protect access. */ -static inline void __set_bit(int nr, volatile unsigned long * addr) +static inline void __set_bit(int nr, unsigned long *addr) { __asm__( "btsl %1,%0" - :"=m" (ADDR) + :"=m" (*addr) :"r" (nr)); } @@ -76,11 +74,11 @@ static inline void __set_bit(int nr, volatile unsigned long * addr) * * See __clear_bit() if you do not require the atomic guarantees. */ -static inline void clear_bit(int nr, volatile unsigned long * addr) +static inline void clear_bit(int nr, unsigned long *addr) { __asm__ __volatile__( LOCK_PREFIX "btrl %1,%0" - :"=m" (ADDR) + :"=m" (*addr) :"r" (nr)); } @@ -96,11 +94,11 @@ static inline void clear_bit(int nr, volatile unsigned long * addr) * This is a fast and unlocked operation, and only suitable for callers * that already implement higher-level locking to protect access. */ -static inline void __clear_bit(int nr, volatile unsigned long * addr) +static inline void __clear_bit(int nr, unsigned long *addr) { __asm__ __volatile__( "btrl %1,%0" - :"=m" (ADDR) + :"=m" (*addr) :"r" (nr)); } @@ -123,11 +121,11 @@ static inline void __clear_bit(int nr, volatile unsigned long * addr) * This is a fast and unlocked operation, and only suitable for callers * that already implement higher-level locking to protect access. */ -static inline void __change_bit(int nr, volatile unsigned long * addr) +static inline void __change_bit(int nr, unsigned long *addr) { __asm__ __volatile__( "btcl %1,%0" - :"=m" (ADDR) + :"=m" (*addr) :"r" (nr)); } @@ -141,11 +139,11 @@ static inline void __change_bit(int nr, volatile unsigned long * addr) * * See __change_bit() if you do not require the atomic guarantees. */ -static inline void change_bit(int nr, volatile unsigned long * addr) +static inline void change_bit(int nr, unsigned long *addr) { __asm__ __volatile__( LOCK_PREFIX "btcl %1,%0" - :"=m" (ADDR) + :"=m" (*addr) :"r" (nr)); } @@ -159,13 +157,13 @@ static inline void change_bit(int nr, volatile unsigned long * addr) * * See __test_and_set_bit() if you do not require the atomic guarantees. */ -static inline int test_and_set_bit(int nr, volatile unsigned long * addr) +static inline int test_and_set_bit(int nr, unsigned long *addr) { int oldbit; __asm__ __volatile__( LOCK_PREFIX "btsl %2,%1\n\tsbbl %0,%0" - :"=r" (oldbit),"=m" (ADDR) + :"=r" (oldbit),"=m" (*addr) :"r" (nr) : "memory"); return oldbit; } @@ -182,13 +180,13 @@ static inline int test_and_set_bit(int nr, volatile unsigned long * addr) * This is a fast and unlocked operation, and only suitable for callers * that already implement higher-level locking to protect access. */ -static inline int __test_and_set_bit(int nr, volatile unsigned long * addr) +static inline int __test_and_set_bit(int nr, unsigned long *addr) { int oldbit; __asm__( "btsl %2,%1\n\tsbbl %0,%0" - :"=r" (oldbit),"=m" (ADDR) + :"=r" (oldbit),"=m" (*addr) :"r" (nr)); return oldbit; } @@ -203,13 +201,13 @@ static inline int __test_and_set_bit(int nr, volatile unsigned long * addr) * * See __test_and_clear_bit() if you do not require the atomic guarantees. */ -static inline int test_and_clear_bit(int nr, volatile unsigned long * addr) +static inline int test_and_clear_bit(int nr, unsigned long *addr) { int oldbit; __asm__ __volatile__( LOCK_PREFIX "btrl %2,%1\n\tsbbl %0,%0" - :"=r" (oldbit),"=m" (ADDR) + :"=r" (oldbit),"=m" (*addr) :"r" (nr) : "memory"); return oldbit; } @@ -226,13 +224,13 @@ static inline int test_and_clear_bit(int nr, volatile unsigned long * addr) * This is a fast and unlocked operation, and only suitable for callers * that already implement higher-level locking to protect access. */ -static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr) +static inline int __test_and_clear_bit(int nr, unsigned long *addr) { int oldbit; __asm__( "btrl %2,%1\n\tsbbl %0,%0" - :"=r" (oldbit),"=m" (ADDR) + :"=r" (oldbit),"=m" (*addr) :"r" (nr)); return oldbit; } @@ -249,13 +247,13 @@ static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr) * This is a fast and unlocked operation, and only suitable for callers * that already implement higher-level locking to protect access. */ -static inline int __test_and_change_bit(int nr, volatile unsigned long *addr) +static inline int __test_and_change_bit(int nr, unsigned long *addr) { int oldbit; __asm__ __volatile__( "btcl %2,%1\n\tsbbl %0,%0" - :"=r" (oldbit),"=m" (ADDR) + :"=r" (oldbit),"=m" (*addr) :"r" (nr) : "memory"); return oldbit; } @@ -270,13 +268,13 @@ static inline int __test_and_change_bit(int nr, volatile unsigned long *addr) * * See __test_and_change_bit() if you do not require the atomic guarantees. */ -static inline int test_and_change_bit(int nr, volatile unsigned long* addr) +static inline int test_and_change_bit(int nr, unsigned long *addr) { int oldbit; __asm__ __volatile__( LOCK_PREFIX "btcl %2,%1\n\tsbbl %0,%0" - :"=r" (oldbit),"=m" (ADDR) + :"=r" (oldbit),"=m" (*addr) :"r" (nr) : "memory"); return oldbit; } @@ -287,22 +285,22 @@ static inline int test_and_change_bit(int nr, volatile unsigned long* addr) * @nr: bit number to test * @addr: Address to start counting from */ -static int test_bit(int nr, const volatile void * addr); +static int test_bit(int nr, const unsigned long *addr); #endif -static __always_inline int constant_test_bit(int nr, const volatile unsigned long *addr) +static __always_inline int constant_test_bit(int nr, const unsigned long *addr) { return ((1UL << (nr & 31)) & (addr[nr >> 5])) != 0; } -static inline int variable_test_bit(int nr, const volatile unsigned long * addr) +static inline int variable_test_bit(int nr, const unsigned long *addr) { int oldbit; __asm__ __volatile__( "btl %2,%1\n\tsbbl %0,%0" :"=r" (oldbit) - :"m" (ADDR),"r" (nr)); + :"m" (*addr),"r" (nr)); return oldbit; } @@ -311,8 +309,6 @@ static inline int variable_test_bit(int nr, const volatile unsigned long * addr) constant_test_bit((nr),(addr)) : \ variable_test_bit((nr),(addr))) -#undef ADDR - /** * find_first_zero_bit - find the first zero bit in a memory region * @addr: The address to start the search at - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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