Because with latches there is a strict data dependency on the seq load we can avoid the rmb in favour of a read_barrier_depends. Suggested-by: Ingo Molnar Signed-off-by: Peter Zijlstra (Intel) --- include/linux/seqlock.h | 9 +++++++-- kernel/time/timekeeping.c | 2 +- 2 files changed, 8 insertions(+), 3 deletions(-) --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -35,6 +35,7 @@ #include #include #include +#include #include /* @@ -233,6 +234,11 @@ static inline void raw_write_seqcount_en s->sequence++; } +static inline int raw_read_seqcount_latch(seqcount_t *s) +{ + return lockless_dereference(s->sequence); +} + /** * raw_write_seqcount_latch - redirect readers to even/odd copy * @s: pointer to seqcount_t @@ -284,8 +290,7 @@ static inline void raw_write_seqcount_en * unsigned seq, idx; * * do { - * seq = latch->seq; - * smp_rmb(); + * seq = lockless_dereference(latch->seq); * * idx = seq & 0x01; * entry = data_query(latch->data[idx], ...); --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -393,7 +393,7 @@ static __always_inline u64 __ktime_get_f u64 now; do { - seq = raw_read_seqcount(&tkf->seq); + seq = raw_read_seqcount_latch(&tkf->seq); tkr = tkf->base + (seq & 0x01); now = ktime_to_ns(tkr->base) + timekeeping_get_ns(tkr); } while (read_seqcount_retry(&tkf->seq, seq)); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/