On Wed, Jun 12, 2024 at 03:37:55PM -0700, Paul E. McKenney wrote: > On Wed, Jun 12, 2024 at 02:33:05PM -0700, Jakub Kicinski wrote: > > On Sun, 9 Jun 2024 10:27:12 +0200 Julia Lawall wrote: > > > Since SLOB was removed, it is not necessary to use call_rcu > > > when the callback only performs kmem_cache_free. Use > > > kfree_rcu() directly. > > > > > > The changes were done using the following Coccinelle semantic patch. > > > This semantic patch is designed to ignore cases where the callback > > > function is used in another way. > > > > How does the discussion on: > > [PATCH] Revert "batman-adv: prefer kfree_rcu() over call_rcu() with free-only callbacks" > > https://lore.kernel.org/all/20240612133357.2596-1-linus.luessing@xxxxxxxxx/ > > reflect on this series? IIUC we should hold off.. > > We do need to hold off for the ones in kernel modules (such as 07/14) > where the kmem_cache is destroyed during module unload. > > OK, I might as well go through them... > > [PATCH 01/14] wireguard: allowedips: replace call_rcu by kfree_rcu for simple kmem_cache_free callback > Needs to wait, see wg_allowedips_slab_uninit(). Also, notably, this patch needs additionally: diff --git a/drivers/net/wireguard/allowedips.c b/drivers/net/wireguard/allowedips.c index e4e1638fce1b..c95f6937c3f1 100644 --- a/drivers/net/wireguard/allowedips.c +++ b/drivers/net/wireguard/allowedips.c @@ -377,7 +377,6 @@ int __init wg_allowedips_slab_init(void) void wg_allowedips_slab_uninit(void) { - rcu_barrier(); kmem_cache_destroy(node_cache); } Once kmem_cache_destroy has been fixed to be deferrable. I assume the other patches are similar -- an rcu_barrier() can be removed. So some manual meddling of these might be in order. Jason
