linux-kernel - [PATCH v2 2/2] mm/slab: break up RCU readers on SLAB_TYPESAFE_BY

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Date:   Sat, 15 Apr 2023 03:31:59 +0000
From:   SeongJae Park <sj@...nel.org>
To:     akpm@...ux-foundation.org
Cc:     vbabka@...e.cz, willy@...radead.org, paulmck@...nel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        SeongJae Park <sj@...nel.org>
Subject: [PATCH v2 2/2] mm/slab: break up RCU readers on SLAB_TYPESAFE_BY_RCU example code

The SLAB_TYPESAFE_BY_RCU example code snippet is having not tiny RCU
read-side critical section.  'Documentation/RCU/rculist_nulls.rst' has
similar example code snippet, and commit da82af04352b ("doc: Update and
wordsmith rculist_nulls.rst") has broken it.  Apply the change to
SLAB_TYPESAFE_BY_RCU example code snippet, too.

Signed-off-by: SeongJae Park <sj@...nel.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