[PATCH v2 1/2] locking: Implement an algorithm choice for Wound-Wait mutexes

[Matthew Wilcox]

On Thu, Jun 14, 2018 at 01:54:15PM +0200, Thomas Hellstrom wrote:
> On 06/14/2018 01:36 PM, Peter Zijlstra wrote:
> > Currently you don't allow mixing WD and WW contexts (which is not
> > immediately obvious from the above code), and the above hard relies on
> > that. Are there sensible use cases for mixing them? IOW will your
> > current restriction stand without hassle?
> 
> Contexts _must_ agree on the algorithm used to resolve deadlocks. With
> Wait-Die, for example, older transactions will wait if a lock is held by a
> younger transaction and with Wound-Wait, younger transactions will wait if a
> lock is held by an older transaction so there is no way of mixing them.

Maybe the compiler should be enforcing that; ie make it a different type?