On powerpc, access_ok() succeeds for the NULL pointer. This breaks the
dynamic check in futex_detect_cmpxchg(), which expects -EFAULT. As a
result, robust futex operations are not functional on powerpc.
Since the architecture's futex_atomic_cmpxchg_inatomic() implementation
requires no runtime feature detection, we can select HAVE_FUTEX_CMPXCHG
to skip futex_detect_cmpxchg() and enable the use of robust futexes.
Signed-off-by: Samuel Holland <sam...@sholland.org>
---
arch/powerpc/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ad620637cbd1..5ad1deb0c669 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -196,6 +196,7 @@ config PPC
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
+ select HAVE_FUTEX_CMPXCHG
select HAVE_GCC_PLUGINS if GCC_VERSION >= 50200 #
plugin support on gcc <= 5.1 is buggy on PPC
select HAVE_HW_BREAKPOINT if PERF_EVENTS && (PPC_BOOK3S
|| PPC_8xx)
select HAVE_IDE
--
2.26.2
