From: Jakub Kicinski <kuba@kernel.org>
To: Stanislav Fomichev <sdf@fomichev.me>
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
pabeni@redhat.com, linux-kernel@vger.kernel.org,
jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us,
horms@kernel.org
Subject: Re: [PATCH net-next v2] net: hold netdev reference during qdisc_create request_module
Date: Mon, 24 Mar 2025 15:04:25 -0700 [thread overview]
Message-ID: <20250324150425.32b3ec10@kernel.org> (raw)
In-Reply-To: <20250320165103.3926946-1-sdf@fomichev.me>
On Thu, 20 Mar 2025 09:51:03 -0700 Stanislav Fomichev wrote:
> rtnl_lock();
> netdev_lock_ops(dev);
> + dev_put(dev);
> ops = qdisc_lookup_ops(kind);
I'm not sure if this is a correct sequence. Do we guarantee that locks
will be taken before device is freed? I mean we do:
dev = netdev_wait_allrefs_any()
free_netdev(dev)
mutex_destroy(dev->lock)
without explicitly taking rtnl_lock() or netdev_lock(), so the moment
that dev_put() is called the device may get freed from another thread
- while its locked here.
My mental model is that taking the instance lock on a dev for which we
only have a ref requires a dance implemented in __netdev_put_lock().
next prev parent reply other threads:[~2025-03-24 22:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-20 16:51 [PATCH net-next v2] net: hold netdev reference during qdisc_create request_module Stanislav Fomichev
2025-03-24 22:04 ` Jakub Kicinski [this message]
2025-03-24 22:22 ` Stanislav Fomichev
2025-03-25 10:28 ` Jakub Kicinski
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