On 2023/08/30 20:26, Hillf Danton wrote:

quoted

<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.