[tip: locking/core] seqlock: kernel-doc: Specify when preemption is automatically altered

[tip-bot2 for Ahmed S. Darwish]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     cb262935a166bdef0ccfe6e2adffa00c0f2d038a
Gitweb:        https://git.kernel.org/tip/cb262935a166bdef0ccfe6e2adffa00c0f2d038a
Author:        Ahmed S. Darwish <a.darwish@xxxxxxxxxxxxx>
AuthorDate:    Sun, 06 Dec 2020 17:21:43 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 09 Dec 2020 17:08:49 +01:00

seqlock: kernel-doc: Specify when preemption is automatically altered

The kernel-doc annotations for sequence counters write side functions
are incomplete: they do not specify when preemption is automatically
disabled and re-enabled.

This has confused a number of call-site developers. Fix it.

Signed-off-by: Ahmed S. Darwish <a.darwish@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/CAHk-=wikhGExmprXgaW+MVXG1zsGpztBbVwOb23vetk41EtTBQ@xxxxxxxxxxxxxx
---
 include/linux/seqlock.h | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 235cbc6..2f7bb92 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -456,6 +456,8 @@ static inline int do_read_seqcount_retry(const seqcount_t *s, unsigned start)
 /**
  * raw_write_seqcount_begin() - start a seqcount_t write section w/o lockdep
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
+ *
+ * Context: check write_seqcount_begin()
  */
 #define raw_write_seqcount_begin(s)					\
 do {									\
@@ -475,6 +477,8 @@ static inline void do_raw_write_seqcount_begin(seqcount_t *s)
 /**
  * raw_write_seqcount_end() - end a seqcount_t write section w/o lockdep
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
+ *
+ * Context: check write_seqcount_end()
  */
 #define raw_write_seqcount_end(s)					\
 do {									\
@@ -498,6 +502,7 @@ static inline void do_raw_write_seqcount_end(seqcount_t *s)
  * @subclass: lockdep nesting level
  *
  * See Documentation/locking/lockdep-design.rst
+ * Context: check write_seqcount_begin()
  */
 #define write_seqcount_begin_nested(s, subclass)			\
 do {									\
@@ -519,11 +524,10 @@ static inline void do_write_seqcount_begin_nested(seqcount_t *s, int subclass)
  * write_seqcount_begin() - start a seqcount_t write side critical section
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
  *
- * write_seqcount_begin opens a write side critical section of the given
- * seqcount_t.
- *
- * Context: seqcount_t write side critical sections must be serialized and
- * non-preemptible. If readers can be invoked from hardirq or softirq
+ * Context: sequence counter write side sections must be serialized and
+ * non-preemptible. Preemption will be automatically disabled if and
+ * only if the seqcount write serialization lock is associated, and
+ * preemptible.  If readers can be invoked from hardirq or softirq
  * context, interrupts or bottom halves must be respectively disabled.
  */
 #define write_seqcount_begin(s)						\
@@ -545,7 +549,8 @@ static inline void do_write_seqcount_begin(seqcount_t *s)
  * write_seqcount_end() - end a seqcount_t write side critical section
  * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants
  *
- * The write section must've been opened with write_seqcount_begin().
+ * Context: Preemption will be automatically re-enabled if and only if
+ * the seqcount write serialization lock is associated, and preemptible.
  */
 #define write_seqcount_end(s)						\
 do {									\