• Paul Mackerras's avatar
    lib: Provide generic atomic64_t implementation · 09d4e0ed
    Paul Mackerras authored
    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: default avatarPaul Mackerras <paulus@samba.org>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
atomic64.h 1.8 KB