From d756c74e6f6e76e99f8bffcea57833816dd335b6 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 9 Dec 2020 16:54:41 -0800 Subject: doc: Update RCU requirements RCU_INIT_POINTER() description Back in the day, RCU_INIT_POINTER() was the only way to avoid memory-barrier instructions while storing NULL to an RCU-protected pointer. Fortunately, in 2016, rcu_assign_pointer() started checking for compile-time NULL pointers and omitting the memory-barrier instructions in that case. Unfortunately, RCU's Requirements.rst document was not updated accordingly. This commit therefore at long last carries out that update. Fixes: 3a37f7275cda ("rcu: No ordering for rcu_assign_pointer() of NULL") Link: https://lore.kernel.org/lkml/20201209230755.GV7338@casper.infradead.org/ Reported-by: Matthew Wilcox Acked-by: Linus Torvalds Signed-off-by: Paul E. McKenney --- Documentation/RCU/Design/Requirements/Requirements.rst | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'Documentation/RCU') diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst index f32f8faddc7d..65c7839114a5 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.rst +++ b/Documentation/RCU/Design/Requirements/Requirements.rst @@ -1668,8 +1668,7 @@ against mishaps and misuse: this purpose. #. It is not necessary to use rcu_assign_pointer() when creating linked structures that are to be published via a single external - pointer. The RCU_INIT_POINTER() macro is provided for this task - and also for assigning ``NULL`` pointers at runtime. + pointer. The RCU_INIT_POINTER() macro is provided for this task. This not a hard-and-fast list: RCU's diagnostic capabilities will continue to be guided by the number and type of usage bugs found in -- cgit v1.2.3