[FS#804] mt7621: kernel errors - rcu_sched detected stalls on CPUs/tasks

[LEDE Bugs]

The following task has a new comment added:

FS#804 - mt7621: kernel errors - rcu_sched detected stalls on CPUs/tasks
User who did this - Pierre Parent (pparent76)

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Not sure if it is related but today I got with latest version:

[  281.257967] BUG: Bad page map in process hotplug-call  pte:00ffffff pmd:00000000
[  281.267040] page:81022fe0 count:0 mapcount:-1 mapping:  (null) index:0x0[  281.271831] device br-lan entered promiscuous mode
[  281.278495] flags: 0x14(referenced|dirty)
[  281.282487] page dumped because: bad pte
[  281.286439] addr:77e78000 vm_flags:00100077 anon_vma:8e8dd9d8 mapping:8f85ca0c index:12
[  281.294460] file:libgcc_s.so.1 fault:filemap_fault mmap:generic_file_readonly_mmap readpage:squashfs_readpage
[  281.304379] CPU: 3 PID: 21248 Comm: hotplug-call Not tainted 4.9.49 #0
[  281.310880] Stack : 00000000 00000000 80557b2a 0000003a 80406a44 00000000 00000000 80550000
[  281.319232]         8fd988fc 804ebea7 80482a8c 00000003 00005300 80553824 8f85ca0c 804e90c0
[  281.327580]         804e90c0 8006b878 00000000 8006b698 00000000 00000001 80487674 8e869bd4
[  281.335926]         00000000 800a9fe0 00000000 00000000 80557b2a 00000000 8f85ca0c 00869bd4
[  281.344268]         00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[  281.352612]         ...
[  281.355051] Call Trace:
[  281.357509] [] show_stack+0x54/0x88
[  281.361864] [] dump_stack+0x8c/0xd0
[  281.366213] [] print_bad_pte+0x1d8/0x208
[  281.370983] [] unmap_page_range+0x5a4/0x760
[  281.376013] [] unmap_vmas+0x54/0x74
[  281.380358] [] exit_mmap+0x6c/0x138
[  281.384696] [] mmput+0x44/0x120
[  281.388708] [] flush_old_exec+0x59c/0x740
[  281.393587] [] load_elf_binary+0x3d4/0x1174
[  281.398618] [] search_binary_handler+0xc4/0x25c
[  281.403991] [] do_execveat_common+0x490/0x600
[  281.409302] Disabling lock debugging due to kernel taint
[  281.414938] BUG: Bad rss-counter state mm:8eaf8700 idx:0 val:-1
[  281.420833] BUG: Bad rss-counter state mm:8eaf8700 idx:1 val:1

After that the router did not respond, even in UART until I rebooted it.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=804#comment3484