lkml.org 
[lkml]   [2022]   [Aug]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH rcu 1/7] doc: Emphasize the need for explicit RCU read-side markers
Date
This commit updates checklist.rst to emphasize the need for explicit
markers for RCU read-side critical sections.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/RCU/checklist.rst | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/Documentation/RCU/checklist.rst b/Documentation/RCU/checklist.rst
index 42cc5d891bd26..5eedef027d922 100644
--- a/Documentation/RCU/checklist.rst
+++ b/Documentation/RCU/checklist.rst
@@ -66,8 +66,13 @@ over a rather long period of time, but improvements are always welcome!
As a rough rule of thumb, any dereference of an RCU-protected
pointer must be covered by rcu_read_lock(), rcu_read_lock_bh(),
rcu_read_lock_sched(), or by the appropriate update-side lock.
- Disabling of preemption can serve as rcu_read_lock_sched(), but
- is less readable and prevents lockdep from detecting locking issues.
+ Explicit disabling of preemption (preempt_disable(), for example)
+ can serve as rcu_read_lock_sched(), but is less readable and
+ prevents lockdep from detecting locking issues.
+
+ Please not that you *cannot* rely on code known to be built
+ only in non-preemptible kernels. Such code can and will break,
+ especially in kernels built with CONFIG_PREEMPT_COUNT=y.

Letting RCU-protected pointers "leak" out of an RCU read-side
critical section is every bit as bad as letting them leak out
--
2.31.1.189.g2e36527f23
\
 
 \ /
  Last update: 2022-08-31 20:07    [W:0.041 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site