diff options
Diffstat (limited to 'include/linux/seqlock.h')
| -rw-r--r-- | include/linux/seqlock.h | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index c6db9fb33c4..600060e25ec 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -141,7 +141,7 @@ static inline unsigned __read_seqcount_begin(const seqcount_t *s) unsigned ret; repeat: - ret = s->sequence; + ret = ACCESS_ONCE(s->sequence); if (unlikely(ret & 1)) { cpu_relax(); goto repeat; @@ -166,6 +166,27 @@ static inline unsigned read_seqcount_begin(const seqcount_t *s) } /** + * raw_seqcount_begin - begin a seq-read critical section + * @s: pointer to seqcount_t + * Returns: count to be passed to read_seqcount_retry + * + * raw_seqcount_begin opens a read critical section of the given seqcount. + * Validity of the critical section is tested by checking read_seqcount_retry + * function. + * + * Unlike read_seqcount_begin(), this function will not wait for the count + * to stabilize. If a writer is active when we begin, we will fail the + * read_seqcount_retry() instead of stabilizing at the beginning of the + * critical section. + */ +static inline unsigned raw_seqcount_begin(const seqcount_t *s) +{ + unsigned ret = ACCESS_ONCE(s->sequence); + smp_rmb(); + return ret & ~1; +} + +/** * __read_seqcount_retry - end a seq-read critical section (without barrier) * @s: pointer to seqcount_t * @start: count, from read_seqcount_begin |