lib: Provide generic atomic64_t implementation

2009-06-15T03:27:38Z

Many processor architectures have no 64-bit atomic instructions, but we need atomic64_t in order to support the perf_counter subsystem. This adds an implementation of 64-bit atomic operations using hashed spinlocks to provide atomicity. For each atomic operation, the address of the atomic64_t variable is hashed to an index into an array of 16 spinlocks. That spinlock is taken (with interrupts disabled) around the operation, which can then be coded non-atomically within the lock. On UP, all the spinlock manipulation goes away and we simply disable interrupts around each operation. In fact gcc eliminates the whole atomic64_lock variable as well. Signed-off-by: Paul Mackerras Signed-off-by: Benjamin Herrenschmidt

linux/include/asm-generic/atomic64.h, branch v3.4-rc2

lib: Provide generic atomic64_t implementation