netdev - Re: [PATCH v2 net-next 06/14] netlink: hold nlk->cb_mutex longer in __netlink_dump

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Date: Sun, 9 Jun 2024 17:29:08 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Jiri Pirko <jiri@...nulli.us>, Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        netdev@...r.kernel.org, Ido Schimmel <idosch@...dia.com>,
        Jiri Pirko <jiri@...dia.com>, eric.dumazet@...il.com
Subject: Re: [PATCH v2 net-next 06/14] netlink: hold nlk->cb_mutex longer in
 __netlink_dump_start()

On 2024/06/09 17:17, Tetsuo Handa wrote:
> Hello.
> 
> While investigating hung task reports involving rtnl_mutex, I came to
> suspect that commit b5590270068c ("netlink: hold nlk->cb_mutex longer
> in __netlink_dump_start()") is buggy, for that commit made only
> mutex_lock(nlk->cb_mutex) side conditionally. Why don't we need to make
> mutex_unlock(nlk->cb_mutex) side conditionally?
> 

Sorry for the noise. That commit should be correct, for the caller
no longer calls mutex_unlock(nlk->cb_mutex).

I'll try a debug printk() patch for linux-next.