linux-kernel - Re: selftests: net: pmtu.sh: Unable to handle kernel paging request at virtual address

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Date:   Wed, 30 Aug 2023 21:44:57 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Hillf Danton <hdanton@...a.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     Netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: selftests: net: pmtu.sh: Unable to handle kernel paging request
 at virtual address

On 2023/08/30 20:26, Hillf Danton wrote:
>> <4>[  399.014716] Call trace:
>> <4>[  399.015702]  percpu_counter_add_batch+0x28/0xd0
>> <4>[  399.016399]  dst_destroy+0x44/0x1e4
>> <4>[  399.016681]  dst_destroy_rcu+0x14/0x20
>> <4>[  399.017009]  rcu_core+0x2d0/0x5e0
>> <4>[  399.017311]  rcu_core_si+0x10/0x1c
>> <4>[  399.017609]  __do_softirq+0xd4/0x23c
>> <4>[  399.017991]  ____do_softirq+0x10/0x1c
>> <4>[  399.018320]  call_on_irq_stack+0x24/0x4c
>> <4>[  399.018723]  do_softirq_own_stack+0x1c/0x28
>> <4>[  399.022639]  __irq_exit_rcu+0x6c/0xcc
>> <4>[  399.023434]  irq_exit_rcu+0x10/0x1c
>> <4>[  399.023962]  el1_interrupt+0x8c/0xc0
>> <4>[  399.024810]  el1h_64_irq_handler+0x18/0x24
>> <4>[  399.025324]  el1h_64_irq+0x64/0x68
>> <4>[  399.025612]  _raw_spin_lock_bh+0x0/0x6c
>> <4>[  399.026102]  cleanup_net+0x280/0x45c
>> <4>[  399.026403]  process_one_work+0x1d4/0x310
>> <4>[  399.027140]  worker_thread+0x248/0x470
>> <4>[  399.027621]  kthread+0xfc/0x184
>> <4>[  399.028068]  ret_from_fork+0x10/0x20
> 
> static void cleanup_net(struct work_struct *work)
> {
> 	...
> 
> 	synchronize_rcu();
> 
> 	/* Run all of the network namespace exit methods */
> 	list_for_each_entry_reverse(ops, &pernet_list, list)
> 		ops_exit_list(ops, &net_exit_list);
> 	...
> 
> Why did the RCU sync above fail to work in this report, Eric?

Why do you assume that synchronize_rcu() failed to work?
The trace merely says that an interrupt handler ran somewhere from
cleanup_net(), and something went wrong inside dst_destroy().

Please decode the trace into filename:line format (like syzbot reports)
using scripts/faddr2line tool, in order to find the exact location.