From: Eric Dumazet <edumazet@google.com>
To: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>
Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com,
Eric Dumazet <edumazet@google.com>
Subject: [PATCH net-next] net: give more chances to rcu in netdev_wait_allrefs_any()
Date: Fri, 26 Apr 2024 06:42:22 +0000 [thread overview]
Message-ID: <20240426064222.1152209-1-edumazet@google.com> (raw)
This came while reviewing commit c4e86b4363ac ("net: add two more
call_rcu_hurry()").
Paolo asked if adding one synchronize_rcu() would help.
While synchronize_rcu() does not help, making sure to call
rcu_barrier() before msleep(wait) is definitely helping
to make sure lazy call_rcu() are completed.
Instead of waiting ~100 seconds in my tests, the ref_tracker
splats occurs one time only, and netdev_wait_allrefs_any()
latency is reduced to the strict minimum.
Ideally we should audit our call_rcu() users to make sure
no refcount (or cascading call_rcu()) is held too long,
because rcu_barrier() is quite expensive.
Fixes: 0e4be9e57e8c ("net: use exponential backoff in netdev_wait_allrefs")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/all/28bbf698-befb-42f6-b561-851c67f464aa@kernel.org/T/#m76d73ed6b03cd930778ac4d20a777f22a08d6824
---
net/core/dev.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index e09aa3785c159b4ab0fe7eb3546f9dd6797ebce2..c9e59eff8ec841f6267c2749489fdc7fe0d03430 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10566,8 +10566,9 @@ static struct net_device *netdev_wait_allrefs_any(struct list_head *list)
rebroadcast_time = jiffies;
}
+ rcu_barrier();
+
if (!wait) {
- rcu_barrier();
wait = WAIT_REFS_MIN_MSECS;
} else {
msleep(wait);
--
2.44.0.769.g3c40516874-goog
next reply other threads:[~2024-04-26 6:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 6:42 Eric Dumazet [this message]
2024-04-26 11:34 ` [PATCH net-next] net: give more chances to rcu in netdev_wait_allrefs_any() Jiri Pirko
2024-04-29 9:00 ` patchwork-bot+netdevbpf
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