[PATCH v4 0/2] mm/slab: trivial fixup for SLAB_TYPESAFE_BY_RCU example code snippet

[PATCH v4 0/2] mm/slab: trivial fixup for SLAB_TYPESAFE_BY_RCU example code snippet

[SeongJae Park]

Changes from v3
(https://lore.kernel.org/linux-mm/20230417173238.22237-1-sj@kernel.org/)
- Yet more wordsmith of the second patch's commit message
  (Matthew Wilcox)

Changes from v2
(https://lore.kernel.org/linux-mm/20230415033159.4249-1-sj@kernel.org/)
- Wordsmith commit message of the second patch (Valstimil Babka)

Changes from v1
(https://lore.kernel.org/linux-mm/20230415003754.1852-1-sj@kernel.org/)
- Update label (s/again/begin/) correctly (Matthew Wilcox)
- Add missed rcu_read_unlock()

This patchset is for trivial fixup for SLAB_TYPESAFE_BY_RCU example code
snippet, namely adding missed semicolon and breaking RCU read-side
critical section into smaller ones.

SeongJae Park (2):
  mm/slab: add a missing semicolon on SLAB_TYPESAFE_BY_RCU example code
  mm/slab: break up RCU readers on SLAB_TYPESAFE_BY_RCU example code

 include/linux/slab.h | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

-- 
2.25.1

[PATCH v4 1/2] mm/slab: add a missing semicolon on SLAB_TYPESAFE_BY_RCU example code

[SeongJae Park]

An example code snippet for SLAB_TYPESAFE_BY_RCU is missing a semicolon.
Add it.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/slab.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index f8b1d63c63a3..b18e56c6f06c 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -53,7 +53,7 @@
  * stays valid, the trick to using this is relying on an independent
  * object validation pass. Something like:
  *
- *  rcu_read_lock()
+ *  rcu_read_lock();
  * again:
  *  obj = lockless_lookup(key);
  *  if (obj) {
-- 
2.25.1

[PATCH v4 2/2] mm/slab: break up RCU readers on SLAB_TYPESAFE_BY_RCU example code

[SeongJae Park]

The SLAB_TYPESAFE_BY_RCU example code snippet uses a single RCU
read-side critical section for retries.
'Documentation/RCU/rculist_nulls.rst' has similar example code snippet,
and commit da82af04352b ("doc: Update and wordsmith rculist_nulls.rst")
broke it up.  Apply the change to SLAB_TYPESAFE_BY_RCU example code
snippet, too.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 include/linux/slab.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index b18e56c6f06c..6acf1b7c6551 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -53,16 +53,18 @@
  * stays valid, the trick to using this is relying on an independent
  * object validation pass. Something like:
  *
+ * begin:
  *  rcu_read_lock();
- * again:
  *  obj = lockless_lookup(key);
  *  if (obj) {
  *    if (!try_get_ref(obj)) // might fail for free objects
- *      goto again;
+ *      rcu_read_unlock();
+ *      goto begin;
  *
  *    if (obj->key != key) { // not the object we expected
  *      put_ref(obj);
- *      goto again;
+ *      rcu_read_unlock();
+ *      goto begin;
  *    }
  *  }
  *  rcu_read_unlock();
-- 
2.25.1

Re: [PATCH v4 2/2] mm/slab: break up RCU readers on SLAB_TYPESAFE_BY_RCU example code

[Paul E. McKenney]

On Mon, Apr 17, 2023 at 07:04:50PM +0000, SeongJae Park wrote:
> The SLAB_TYPESAFE_BY_RCU example code snippet uses a single RCU
> read-side critical section for retries.
> 'Documentation/RCU/rculist_nulls.rst' has similar example code snippet,
> and commit da82af04352b ("doc: Update and wordsmith rculist_nulls.rst")
> broke it up.  Apply the change to SLAB_TYPESAFE_BY_RCU example code
> snippet, too.
> 
> Signed-off-by: SeongJae Park <sj@kernel.org>

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>

> ---
>  include/linux/slab.h | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index b18e56c6f06c..6acf1b7c6551 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -53,16 +53,18 @@
>   * stays valid, the trick to using this is relying on an independent
>   * object validation pass. Something like:
>   *
> + * begin:
>   *  rcu_read_lock();
> - * again:
>   *  obj = lockless_lookup(key);
>   *  if (obj) {
>   *    if (!try_get_ref(obj)) // might fail for free objects
> - *      goto again;
> + *      rcu_read_unlock();
> + *      goto begin;
>   *
>   *    if (obj->key != key) { // not the object we expected
>   *      put_ref(obj);
> - *      goto again;
> + *      rcu_read_unlock();
> + *      goto begin;
>   *    }
>   *  }
>   *  rcu_read_unlock();
> -- 
> 2.25.1
> 

Re: [PATCH v4 0/2] mm/slab: trivial fixup for SLAB_TYPESAFE_BY_RCU example code snippet

[Vlastimil Babka]

On 4/17/23 21:04, SeongJae Park wrote:
> Changes from v3
> (https://lore.kernel.org/linux-mm/20230417173238.22237-1-sj@kernel.org/)
> - Yet more wordsmith of the second patch's commit message
>   (Matthew Wilcox)
> 
> Changes from v2
> (https://lore.kernel.org/linux-mm/20230415033159.4249-1-sj@kernel.org/)
> - Wordsmith commit message of the second patch (Valstimil Babka)
> 
> Changes from v1
> (https://lore.kernel.org/linux-mm/20230415003754.1852-1-sj@kernel.org/)
> - Update label (s/again/begin/) correctly (Matthew Wilcox)
> - Add missed rcu_read_unlock()
> 
> This patchset is for trivial fixup for SLAB_TYPESAFE_BY_RCU example code
> snippet, namely adding missed semicolon and breaking RCU read-side
> critical section into smaller ones.

Oops, almost forgot to merge this, now done, with Paul's R-b's, in
slab/for-6.5/cleanup. Thanks!

> SeongJae Park (2):
>   mm/slab: add a missing semicolon on SLAB_TYPESAFE_BY_RCU example code
>   mm/slab: break up RCU readers on SLAB_TYPESAFE_BY_RCU example code
> 
>  include/linux/slab.h | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>