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From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Cc:     linux-rt-users <linux-rt-users@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        stable-rt@vger.kernel.org, Chunyu Hu <chuhu@redhat.com>
Subject: Re: [RFC RT v5.10] [rt] repair usage of raw_v6_hashinfo.lock in
 raw_seq_start()
Message-ID: <20211011163333.2o64amr4qks4gpdm@linutronix.de>
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On 2021-10-04 22:53:08 [-0300], Luis Claudio R. Goncalves wrote:
> Avoid a possible circular locking dependency by taking the softirq_ctrl.lock
> before taking raw_v6_hashinfo.lock in raw_seq_start(), keeping locking order
> consistent.

How do you reproduce this one? It does not trigger here. Maybe I'm doing
something wrong. The command
	hping3 -C 3 -K 1 -c 1 $ip

triggers raw_icmp_error() from within the softirq processing. And
	cat /proc/net/raw

does raw_seq_start(). No BH here. Additionally during boot raw_hash_sk()
is invoked from non-BH context here but it is a write-lock so it has to
disable BH since there is at least one reader in BH.

The ipv4 code looks close to the ipv6. The problem is that hping does
not support v6 :/ Maybe the ipv6 acquires a bh lock somewhere which
leads to this.

Sebastian