On Fri, Aug 07, 2015 at 04:13:03PM +0100, Peter Zijlstra wrote:

On Thu, Aug 06, 2015 at 05:54:36PM +0100, Will Deacon wrote:

quoted

The series adds support for a family of relaxed atomics to the kernel.
More specifically:

  - acquire/release/relaxed flavours of xchg, cmpxchg and {add,sub}_return
  - atomic_read_acquire
  - atomic_set_release

This came out of a separate patch series porting the (barrier-heavy)
qrwlock code to arm64. Rather than have arch-specific hooks littered
around the place, it makes more sense to define a core set of relaxed
atomics that can be used regardless of architecture.

Changes since v4 are:

  * Drop the ret_t macro parameter in favour of typeof tricks (Peter Z)

  * Add a missing acquire to the qrwlock code, as it was based on a
    previous patch that I posted (Waiman Long)

Build tested on ARM, arm64, PowerPC and x86.

Queued it. There was a wee conflict with the atomic_{and,or,xor} bits
for the ARM patch, but that was quickly sorted.

Great, thanks Peter! I'll port arm64 over for 4.4 (there's way too much
fun being had in asm/atomic.h right now).

Does we want a Documentation/ update to reflect all this shiny new
stuff?

Possibly. atomic_ops or memory-barriers?

Will