[RFC PATCH] lib: Introduce generic __cmpxchg_u64() and use it where needed

[Paul E. McKenney]

On Thu, Nov 01, 2018 at 10:38:34PM +0100, Peter Zijlstra wrote:
> On Thu, Nov 01, 2018 at 01:29:10PM -0700, Paul E. McKenney wrote:
> > On Thu, Nov 01, 2018 at 06:27:39PM +0100, Peter Zijlstra wrote:
> > > On Thu, Nov 01, 2018 at 06:14:32PM +0100, Peter Zijlstra wrote:
> > > > > This reminds me of this sooooo silly patch :/
> > > > > 
> > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=adb03115f4590baa280ddc440a8eff08a6be0cb7
> > > 
> > > You'd probably want to write it like so; +- some ordering stuff, that
> > > code didn't look like it really needs the memory barriers implied by
> > > these, but I didn't look too hard.
> > 
> > The atomic_fetch_add() API would need to be propagated out to the other
> > architectures, correct?
> 
> Like these commits I did like 2 years ago ? :-)

Color me blind and stupid!  ;-)

							Thanx, Paul

> $ git log --oneline 6dc25876cdb1...1f51dee7ca74
> 6dc25876cdb1 locking/atomic, arch/xtensa: Implement atomic_fetch_{add,sub,and,or,xor}()
> a8bcccaba162 locking/atomic, arch/x86: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> 1af5de9af138 locking/atomic, arch/tile: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> 3a1adb23a52c locking/atomic, arch/sparc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> 7d9794e75237 locking/atomic, arch/sh: Implement atomic_fetch_{add,sub,and,or,xor}()
> 56fefbbc3f13 locking/atomic, arch/s390: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> a28cc7bbe8e3 locking/atomic, arch/powerpc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}{,_relaxed,_acquire,_release}()
> e5857a6ed600 locking/atomic, arch/parisc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> f8d638e28d7c locking/atomic, arch/mn10300: Implement atomic_fetch_{add,sub,and,or,xor}()
> 4edac529eb62 locking/atomic, arch/mips: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> e898eb27ffd8 locking/atomic, arch/metag: Implement atomic_fetch_{add,sub,and,or,xor}()
> e39d88ea3ce4 locking/atomic, arch/m68k: Implement atomic_fetch_{add,sub,and,or,xor}()
> f64937052303 locking/atomic, arch/m32r: Implement atomic_fetch_{add,sub,and,or,xor}()
> cc102507fac7 locking/atomic, arch/ia64: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> 4be7dd393515 locking/atomic, arch/hexagon: Implement atomic_fetch_{add,sub,and,or,xor}()
> 0c074cbc3309 locking/atomic, arch/h8300: Implement atomic_fetch_{add,sub,and,or,xor}()
> d9c730281617 locking/atomic, arch/frv: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
> e87fc0ec0705 locking/atomic, arch/blackfin: Implement atomic_fetch_{add,sub,and,or,xor}()
> 1a6eafacd481 locking/atomic, arch/avr32: Implement atomic_fetch_{add,sub,and,or,xor}()
> 2efe95fe6952 locking/atomic, arch/arm64: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}() for LSE instructions
> 6822a84dd4e3 locking/atomic, arch/arm64: Generate LSE non-return cases using common macros
> e490f9b1d3b4 locking/atomic, arch/arm64: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()
> 6da068c1beba locking/atomic, arch/arm: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()
> fbffe892e525 locking/atomic, arch/arc: Implement atomic_fetch_{add,sub,and,andnot,or,xor}()
>