aboutsummaryrefslogtreecommitdiff
path: root/include/linux/seqlock.h
diff options
context:
space:
mode:
authorAl Viro <viro@zeniv.linux.org.uk>2013-10-25 16:39:14 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2013-11-15 22:04:17 -0500
commit2bc74feba12fbf052ec97aee8624c9f13593a9ac (patch)
tree411129cf4fe962f1afc2c9bca127d9db0924fbfd /include/linux/seqlock.h
parentb26d4cd385fc51e8844e2cdf9ba2051f5bba11a5 (diff)
downloadlinux-2bc74feba12fbf052ec97aee8624c9f13593a9ac.tar.gz
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/seqlock.h')
-rw-r--r--include/linux/seqlock.h29
1 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 1e8a8b6e837..cf87a24c0f9 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);