commit 4badad352a6bb202ec68afa7a574c0bb961e5ebc (locking/mutex: Disable optimistic spinning on some architectures) fenced spinning for architectures without proper cmpxchg. There is no need to disable mutex spinning on s390, though: The instructions CS,CSG and friends provide the proper guarantees. (We dont implement cmpxchg with locks).
Please note: This is a quick fix for s390, suitable for stable as 3.16 unintenionally disabled optimistic spinning. The proper fix is probably to use ARCH_HAVE_NMI_SAFE_CMPXCHG instead of introducing ARCH_SUPPORTS_ATOMIC_RMW. Signed-off-by: Christian Borntraeger <[email protected]> CC: <[email protected]> CC: Peter Zijlstra <[email protected]> CC: [email protected] --- arch/s390/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 9a0ea87..eab3c32 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -63,6 +63,7 @@ config S390 select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS select ARCH_HAVE_NMI_SAFE_CMPXCHG + select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_INLINE_READ_LOCK select ARCH_INLINE_READ_LOCK_BH select ARCH_INLINE_READ_LOCK_IRQ -- 1.8.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
