diff options
author | Al Viro <viro@zeniv.linux.org.uk> | 2013-10-25 20:39:14 (GMT) |
---|---|---|
committer | Al Viro <viro@zeniv.linux.org.uk> | 2013-11-16 03:04:17 (GMT) |
commit | 2bc74feba12fbf052ec97aee8624c9f13593a9ac (patch) | |
tree | 411129cf4fe962f1afc2c9bca127d9db0924fbfd /include/linux | |
parent | b26d4cd385fc51e8844e2cdf9ba2051f5bba11a5 (diff) | |
download | linux-fsl-qoriq-2bc74feba12fbf052ec97aee8624c9f13593a9ac.tar.xz |
take read_seqbegin_or_lock() and friends to seqlock.h
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include/linux')
-rw-r--r-- | include/linux/seqlock.h | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 1e8a8b6..cf87a24 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); |