15 Jun, 2009

1 commit

• 09d4e0edd   lib: Provide generic atomic64_t implementation ... Browse Code »

  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

  Paul Mackerras

  2009-06-15 11:27:38 +0800