The two READ_ONCEs here imply that there might be updater concurrently
modifies rcu_read_lock_nesting, although it's true there could be
interrupt handlers enter rcu RSCS, but rcu_read_lock_nesting should
remain unchanged after they finished. That is, READ_ONCE and then
WRITE_ONCE the same variable is not a valid pattern, this patch thus
removes the two READ_ONCEs.
Signed-off-by: Alan Huang <mmpgouride@xxxxxxxxx>
---
kernel/rcu/tree_plugin.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 340bbefe5f65..c90edbb7fa40 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -376,12 +376,12 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
static void rcu_preempt_read_enter(void)
{
- WRITE_ONCE(current->rcu_read_lock_nesting, READ_ONCE(current->rcu_read_lock_nesting) + 1);
+ WRITE_ONCE(current->rcu_read_lock_nesting, current->rcu_read_lock_nesting + 1);
}
static int rcu_preempt_read_exit(void)
{
- int ret = READ_ONCE(current->rcu_read_lock_nesting) - 1;
+ int ret = current->rcu_read_lock_nesting - 1;
WRITE_ONCE(current->rcu_read_lock_nesting, ret);
return ret;
--
2.34.1
