From: Alexander Aring <aahringo@redhat.com>
To: teigland@redhat.com
Cc: gfs2@lists.linux.dev, aahringo@redhat.com
Subject: [PATCH dlm/next] dlm: add rcu_barrier before destroy kmem cache
Date: Thu, 13 Jun 2024 13:06:40 -0400 [thread overview]
Message-ID: <20240613170640.3556585-1-aahringo@redhat.com> (raw)
In the case we trigger dlm_free_rsb() that does a call_rcu() and the
responding kfree() of res_lvbptr and a kmem_cache_free() of the rsb
pointer we need to wait until this pending operation is done before
calling kmem_cache_destroy(). We doing that by using rcu_barrier() that
waits until all pending call_rcu() are done. This avoids that
kmem_cache_destroy() complains about active objects around that are not
being freed yet by call_rcu().
There is currently more discussions about to make this behaviour better,
see:
https://lore.kernel.org/netdev/20240609082726.32742-1-Julia.Lawall@inria.fr/
However this is only for call_rcu() if the callback calls
kmem_cache_destroy() only to replace it by kfree_rcu() call which has
currently some issue. This isn't our case because we also free the
res_lvbptr if being set.
For our case, to avoid the above race rcu_barrier() should be used before
calling kmem_cache_destroy() to be sure that there are no active objects
around. This is exactly what net/batman-adv is also doing before calling their
kmem_cache_destroy() in module unloading.
Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
fs/dlm/memory.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/dlm/memory.c b/fs/dlm/memory.c
index 105a79978706..8c44b954c166 100644
--- a/fs/dlm/memory.c
+++ b/fs/dlm/memory.c
@@ -72,6 +72,8 @@ int __init dlm_memory_init(void)
void dlm_memory_exit(void)
{
+ rcu_barrier();
+
kmem_cache_destroy(writequeue_cache);
kmem_cache_destroy(mhandle_cache);
kmem_cache_destroy(msg_cache);
--
2.43.0
next reply other threads:[~2024-06-13 17:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-13 17:06 Alexander Aring [this message]
2024-06-13 17:24 ` [PATCH dlm/next] dlm: add rcu_barrier before destroy kmem cache Alexander Aring
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