Please have a look at the patch below. Taking this opportunity, in addition: - I removed the useless "volatile" stuff from the non-atomic versions of the bit operations. - I removed the unnecessary barrier() from __clear_bit_unlock(). ia64_st4_rel_nta() makes sure all the modifications are globally seen before the bit is seen to be off. - I made __clear_bit() modeled after __set_bit() and __change_bit(). - I corrected some comments sating that a memory barrier is provided, yet in reality, it is the acquisition side of the memory barrier only. - I corrected some comments, e.g. test_and_clear_bit() was peaking about "bit to set".
Signed-off-by: Zoltan Menyhart, <[EMAIL PROTECTED]> Thanks, Zoltan Menyhart
--- include/asm/bitops.h-old 2007-12-21 02:25:48.000000000 +0100 +++ include/asm/bitops.h 2008-01-03 14:25:17.000000000 +0100 @@ -60,7 +60,7 @@ * may be that only one operation succeeds. */ static __inline__ void -__set_bit (int nr, volatile void *addr) +__set_bit (int nr, void *addr) { *((__u32 *) addr + (nr >> 5)) |= (1 << (nr & 31)); } @@ -122,38 +122,40 @@ } /** - * __clear_bit_unlock - Non-atomically clear a bit with release + * __clear_bit_unlock - Non-atomically clears a bit in memory with release + * @nr: Bit to clear + * @addr: Address to start counting from * - * This is like clear_bit_unlock, but the implementation uses a store + * Similarly to clear_bit_unlock, the implementation uses a store * with release semantics. See also __raw_spin_unlock(). */ static __inline__ void -__clear_bit_unlock(int nr, volatile void *addr) +__clear_bit_unlock(int nr, void *addr) { - __u32 mask, new; - volatile __u32 *m; + __u32 * const m = (__u32 *) addr + (nr >> 5); + __u32 const new = *m & ~(1 << (nr & 31)); - m = (volatile __u32 *)addr + (nr >> 5); - mask = ~(1 << (nr & 31)); - new = *m & mask; - barrier(); ia64_st4_rel_nta(m, new); } /** * __clear_bit - Clears a bit in memory (non-atomic version) + * @nr: the bit to clear + * @addr: the address to start counting from + * + * Unlike clear_bit(), this function is non-atomic and may be reordered. + * If it's called on the same region of memory simultaneously, the effect + * may be that only one operation succeeds. */ static __inline__ void -__clear_bit (int nr, volatile void *addr) +__clear_bit (int nr, void *addr) { - volatile __u32 *p = (__u32 *) addr + (nr >> 5); - __u32 m = 1 << (nr & 31); - *p &= ~m; + *((__u32 *) addr + (nr >> 5)) &= ~(1 << (nr & 31)); } /** * change_bit - Toggle a bit in memory - * @nr: Bit to clear + * @nr: Bit to toggle * @addr: Address to start counting from * * change_bit() is atomic and may not be reordered. @@ -178,7 +180,7 @@ /** * __change_bit - Toggle a bit in memory - * @nr: the bit to set + * @nr: the bit to toggle * @addr: the address to start counting from * * Unlike change_bit(), this function is non-atomic and may be reordered. @@ -186,7 +188,7 @@ * may be that only one operation succeeds. */ static __inline__ void -__change_bit (int nr, volatile void *addr) +__change_bit (int nr, void *addr) { *((__u32 *) addr + (nr >> 5)) ^= (1 << (nr & 31)); } @@ -197,7 +199,7 @@ * @addr: Address to count from * * This operation is atomic and cannot be reordered. - * It also implies a memory barrier. + * It also implies the acquisition side of the memory barrier. */ static __inline__ int test_and_set_bit (int nr, volatile void *addr) @@ -235,7 +237,7 @@ * but actually fail. You must protect multiple accesses with a lock. */ static __inline__ int -__test_and_set_bit (int nr, volatile void *addr) +__test_and_set_bit (int nr, void *addr) { __u32 *p = (__u32 *) addr + (nr >> 5); __u32 m = 1 << (nr & 31); @@ -247,11 +249,11 @@ /** * test_and_clear_bit - Clear a bit and return its old value - * @nr: Bit to set + * @nr: Bit to clear * @addr: Address to count from * * This operation is atomic and cannot be reordered. - * It also implies a memory barrier. + * It also implies the acquisition side of the memory barrier. */ static __inline__ int test_and_clear_bit (int nr, volatile void *addr) @@ -272,7 +274,7 @@ /** * __test_and_clear_bit - Clear a bit and return its old value - * @nr: Bit to set + * @nr: Bit to clear * @addr: Address to count from * * This operation is non-atomic and can be reordered. @@ -280,7 +282,7 @@ * but actually fail. You must protect multiple accesses with a lock. */ static __inline__ int -__test_and_clear_bit(int nr, volatile void * addr) +__test_and_clear_bit(int nr, void * addr) { __u32 *p = (__u32 *) addr + (nr >> 5); __u32 m = 1 << (nr & 31); @@ -292,11 +294,11 @@ /** * test_and_change_bit - Change a bit and return its old value - * @nr: Bit to set + * @nr: Bit to change * @addr: Address to count from * * This operation is atomic and cannot be reordered. - * It also implies a memory barrier. + * It also implies the acquisition side of the memory barrier. */ static __inline__ int test_and_change_bit (int nr, volatile void *addr) @@ -315,8 +317,12 @@ return (old & bit) != 0; } -/* - * WARNING: non atomic version. +/** + * __test_and_change_bit - Change a bit and return its old value + * @nr: Bit to change + * @addr: Address to count from + * + * This operation is non-atomic and can be reordered. */ static __inline__ int __test_and_change_bit (int nr, void *addr)