On 7/18/23 14:32, Paul E. McKenney wrote:
On Tue, Jul 18, 2023 at 10:48:07PM +0800, Alan Huang wrote:
2023年7月18日 21:49，Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> 写道：
On 7/17/23 14:03, Paul E. McKenney wrote:
From: Alan Huang <mmpgouride@xxxxxxxxx>
When the objects managed by rculist_nulls are allocated with
SLAB_TYPESAFE_BY_RCU, old readers may still hold references to an object
even though it is just now being added, which means the modification of
->next is visible to readers. This patch therefore uses WRITE_ONCE()
for assignments to ->next.
Signed-off-by: Alan Huang <mmpgouride@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Did we ever conclude that the READ_ONCE() counterparts were not needed? ;-)
Read-side is already protected by rcu_dereference_raw() in hlist_nulls_for_each_entry_{rcu, safe}.
It turns out that different traversal synchronization designs want
different pointers using WRITE_ONCE().
Thank you Alan and Paul,
Btw, I don't see any users of hlist_nulls_unhashed_lockless(), maybe it
can be removed?
- Joel
