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Message-ID: <20171023142555.GF3165@worktop.lehotels.local>
Date: Mon, 23 Oct 2017 16:25:55 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: David Miller <davem@...emloft.net>
Cc: fw@...len.de, netdev@...r.kernel.org
Subject: problem with rtnetlink 'reference' count
Hi,
I just ran across commit:
019a316992ee ("rtnetlink: add reference counting to prevent module unload while dump is in progress")
And that commit is _completely_ broken.
1) it not in fact a refcount, so using refcount_t is silly
2) there is a distinct lack of memory barriers, so we can easily
observe the decrement while the msg_handler is still in progress.
3) waiting with a schedule()/yield() loop is complete crap and subject
life-locks, imagine doing that rtnl_unregister_all() from a RT task.
Please fix..
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