From 2bc74feba12fbf052ec97aee8624c9f13593a9ac Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 25 Oct 2013 16:39:14 -0400 Subject: take read_seqbegin_or_lock() and friends to seqlock.h Signed-off-by: Al Viro --- include/linux/seqlock.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'include/linux/seqlock.h') diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 1e8a8b6e837d..cf87a24c0f92 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -354,6 +354,35 @@ static inline void read_sequnlock_excl(seqlock_t *sl) spin_unlock(&sl->lock); } +/** + * read_seqbegin_or_lock - begin a sequence number check or locking block + * @lock: sequence lock + * @seq : sequence number to be checked + * + * First try it once optimistically without taking the lock. If that fails, + * take the lock. The sequence number is also used as a marker for deciding + * whether to be a reader (even) or writer (odd). + * N.B. seq must be initialized to an even number to begin with. + */ +static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq) +{ + if (!(*seq & 1)) /* Even */ + *seq = read_seqbegin(lock); + else /* Odd */ + read_seqlock_excl(lock); +} + +static inline int need_seqretry(seqlock_t *lock, int seq) +{ + return !(seq & 1) && read_seqretry(lock, seq); +} + +static inline void done_seqretry(seqlock_t *lock, int seq) +{ + if (seq & 1) + read_sequnlock_excl(lock); +} + static inline void read_seqlock_excl_bh(seqlock_t *sl) { spin_lock_bh(&sl->lock); -- cgit v1.2.3-59-g8ed1b