lkml.org 
[lkml]   [2020]   [Apr]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH rcu/dev -fixes 3/4] rcu/tree: Avoid using xchg() in kfree_call_rcu_add_ptr_to_bulk()
Date
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

There is no need to use xchg(), the access is serialized by krcp->lock.
The xchg() function adds some atomic barriers which remain hidden in
x86's disassembly but are visible on ARM for instance.

Replace xchg() with a load + store.

Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/rcu/tree.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index cd61649e1b001..f6eb3aee0935e 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3088,7 +3088,8 @@ kfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp,
/* Check if a new block is required. */
if (!krcp->bhead ||
krcp->bhead->nr_records == KFREE_BULK_MAX_ENTR) {
- bnode = xchg(&krcp->bcached, NULL);
+ bnode = krcp->bcached;
+ krcp->bcached = NULL;
if (!bnode) {
WARN_ON_ONCE(sizeof(struct kfree_rcu_bulk_data) > PAGE_SIZE);

--
2.26.1.301.g55bc3eb7cb9-goog
\
 
 \ /
  Last update: 2020-04-20 17:39    [W:0.113 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site