On Wed, Jun 10, 2015 at 04:58:04PM +0200, Ralf Baechle wrote: > On Mon, Jun 08, 2015 at 03:14:43PM +0200, Xose Vazquez Perez wrote: > > > If there is anything wrong, please report it in this thread: > > https://marc.info/?t=143332955700003 > > > > locking/ cmpxchg-local : TODO | HAVE_CMPXCHG_LOCAL # arch supports the this_cpu_cmpxchg() API > > This one was easy - we have the functions in the code just no "select > HAVE_CMPXCHG_LOCAL" Kconfig. Something's wrong there. The new file Documentation/features/locking/cmpxchg-local/arch-support.txt in linux-next claims correctly that only s390 and x86 define HAVE_CMPXCHG_LOCAL. And a git grep -w cmpxchg_local finds that in addition to these alpha, arm, arm64, avr32, blackfin, c6x, frv, ia64, m32r, m68k, mips, parisc, powerpc, sparc, unicore32 and xtensa define cmpxchg_local. These architectures seem to not define cmpxchg_local in their arch/ dir: arc cris hexagon metag microblaze mn10300 nios2 openrisc score sh tile um Microblaze and nios2 include <asm-generic/cmpxchg.h> into their arch cmpxchg.h so they get a definition of these functions but don't define HAVE_CMPXCHG_LOCAL. Peter Zijlstra said it the local versions are ~ 20 cycles faster on x86 than the "global" version. But I've found one user of cmpxchg_local, mm/vmstat.c and one user of cmpxchg64_local, drivers/iommu/intel-iommu.c. Sure, fixing the issue was trivial for me on MIPS but is having cmpxchg{,64}_local actually worth it? Cheers, Ralf
