Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter

[Peter Zijlstra]

On Thu, Nov 21, 2019 at 10:53:03AM -0800, Fenghua Yu wrote:

> 4. Otherwise, re-calculate addr to point the 32-bit address which contains
>    the bit and operate on the bit. No split lock.

That sounds confused, Even BT{,CRS} have a RmW size. There is no
'operate on the bit'.

Specifically I hard rely on BTSL to be a 32bit RmW, see commit:

  7aa54be29765 ("locking/qspinlock, x86: Provide liveness guarantee")

You might need to read this paper:

  https://www.cl.cam.ac.uk/~pes20/popl17/mixed-size.pdf