Subject: Re: printk() + memory offline deadlock (WAS Re: page_alloc.shuffle=1 + CONFIG_PROVE_LOCKING=y = arm64 hang)

From: Sergey Senozhatsky <[email-masked]>
Date: Mon, 23 Sep 2019 19:21:00 +0900

On (09/18/19 12:10), Qian Cai wrote:
[..]
> > So you have debug objects enabled. Right? This thing does not behave
> > when it comes to printing. debug_objects are slightly problematic.
> 
> Yes, but there is an also a similar splat without the debug_objects. It looks
> like anything try to allocate memory in that path will trigger it anyway.

Appears to be different, yet somehow very familiar.

> [  297.425908] WARNING: possible circular locking dependency detected
> [  297.425908] 5.3.0-next-20190917 #8 Not tainted
> [  297.425909] ------------------------------------------------------
> [  297.425910] test.sh/8653 is trying to acquire lock:
> [  297.425911] ffffffff865a4460 (console_owner){-.-.}, at:
> console_unlock+0x207/0x750
> 
> [  297.425914] but task is already holding lock:
> [  297.425915] ffff88883fff3c58 (&(&zone->lock)->rlock){-.-.}, at:
> __offline_isolated_pages+0x179/0x3e0
> 
> [  297.425919] which lock already depends on the new lock.
> 
> 
> [  297.425920] the existing dependency chain (in reverse order) is:
> 
> [  297.425922] -> #3 (&(&zone->lock)->rlock){-.-.}:
> [  297.425925]        __lock_acquire+0x5b3/0xb40
> [  297.425925]        lock_acquire+0x126/0x280
> [  297.425926]        _raw_spin_lock+0x2f/0x40
> [  297.425927]        rmqueue_bulk.constprop.21+0xb6/0x1160
> [  297.425928]        get_page_from_freelist+0x898/0x22c0
> [  297.425928]        __alloc_pages_nodemask+0x2f3/0x1cd0
> [  297.425929]        alloc_pages_current+0x9c/0x110
> [  297.425930]        allocate_slab+0x4c6/0x19c0
> [  297.425931]        new_slab+0x46/0x70
> [  297.425931]        ___slab_alloc+0x58b/0x960
> [  297.425932]        __slab_alloc+0x43/0x70
> [  297.425933]        __kmalloc+0x3ad/0x4b0
> [  297.425933]        __tty_buffer_request_room+0x100/0x250
> [  297.425934]        tty_insert_flip_string_fixed_flag+0x67/0x110
> [  297.425935]        pty_write+0xa2/0xf0
> [  297.425936]        n_tty_write+0x36b/0x7b0
> [  297.425936]        tty_write+0x284/0x4c0
> [  297.425937]        __vfs_write+0x50/0xa0
> [  297.425938]        vfs_write+0x105/0x290
> [  297.425939]        redirected_tty_write+0x6a/0xc0
> [  297.425939]        do_iter_write+0x248/0x2a0
> [  297.425940]        vfs_writev+0x106/0x1e0
> [  297.425941]        do_writev+0xd4/0x180
> [  297.425941]        __x64_sys_writev+0x45/0x50
> [  297.425942]        do_syscall_64+0xcc/0x76c
> [  297.425943]        entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> [  297.425944] -> #2 (&(&port->lock)->rlock){-.-.}:
> [  297.425946]        __lock_acquire+0x5b3/0xb40
> [  297.425947]        lock_acquire+0x126/0x280
> [  297.425948]        _raw_spin_lock_irqsave+0x3a/0x50
> [  297.425949]        tty_port_tty_get+0x20/0x60
> [  297.425949]        tty_port_default_wakeup+0xf/0x30
> [  297.425950]        tty_port_tty_wakeup+0x39/0x40
> [  297.425951]        uart_write_wakeup+0x2a/0x40
> [  297.425952]        serial8250_tx_chars+0x22e/0x440
> [  297.425952]        serial8250_handle_irq.part.8+0x14a/0x170
> [  297.425953]        serial8250_default_handle_irq+0x5c/0x90
> [  297.425954]        serial8250_interrupt+0xa6/0x130
> [  297.425955]        __handle_irq_event_percpu+0x78/0x4f0
> [  297.425955]        handle_irq_event_percpu+0x70/0x100
> [  297.425956]        handle_irq_event+0x5a/0x8b
> [  297.425957]        handle_edge_irq+0x117/0x370
> [  297.425958]        do_IRQ+0x9e/0x1e0
> [  297.425958]        ret_from_intr+0x0/0x2a
> [  297.425959]        cpuidle_enter_state+0x156/0x8e0
> [  297.425960]        cpuidle_enter+0x41/0x70
> [  297.425960]        call_cpuidle+0x5e/0x90
> [  297.425961]        do_idle+0x333/0x370
> [  297.425962]        cpu_startup_entry+0x1d/0x1f
> [  297.425962]        start_secondary+0x290/0x330
> [  297.425963]        secondary_startup_64+0xb6/0xc0
> 
> [  297.425964] -> #1 (&port_lock_key){-.-.}:
> [  297.425967]        __lock_acquire+0x5b3/0xb40
> [  297.425967]        lock_acquire+0x126/0x280
> [  297.425968]        _raw_spin_lock_irqsave+0x3a/0x50
> [  297.425969]        serial8250_console_write+0x3e4/0x450
> [  297.425970]        univ8250_console_write+0x4b/0x60
> [  297.425970]        console_unlock+0x501/0x750
> [  297.425971]        vprintk_emit+0x10d/0x340
> [  297.425972]        vprintk_default+0x1f/0x30
> [  297.425972]        vprintk_func+0x44/0xd4
> [  297.425973]        printk+0x9f/0xc5
> [  297.425974]        register_console+0x39c/0x520
> [  297.425975]        univ8250_console_init+0x23/0x2d
> [  297.425975]        console_init+0x338/0x4cd
> [  297.425976]        start_kernel+0x534/0x724
> [  297.425977]        x86_64_start_reservations+0x24/0x26
> [  297.425977]        x86_64_start_kernel+0xf4/0xfb
> [  297.425978]        secondary_startup_64+0xb6/0xc0
> 
> [  297.425979] -> #0 (console_owner){-.-.}:
> [  297.425982]        check_prev_add+0x107/0xea0
> [  297.425982]        validate_chain+0x8fc/0x1200
> [  297.425983]        __lock_acquire+0x5b3/0xb40
> [  297.425984]        lock_acquire+0x126/0x280
> [  297.425984]        console_unlock+0x269/0x750
> [  297.425985]        vprintk_emit+0x10d/0x340
> [  297.425986]        vprintk_default+0x1f/0x30
> [  297.425987]        vprintk_func+0x44/0xd4
> [  297.425987]        printk+0x9f/0xc5
> [  297.425988]        __offline_isolated_pages.cold.52+0x2f/0x30a
> [  297.425989]        offline_isolated_pages_cb+0x17/0x30
> [  297.425990]        walk_system_ram_range+0xda/0x160
> [  297.425990]        __offline_pages+0x79c/0xa10
> [  297.425991]        offline_pages+0x11/0x20
> [  297.425992]        memory_subsys_offline+0x7e/0xc0
> [  297.425992]        device_offline+0xd5/0x110
> [  297.425993]        state_store+0xc6/0xe0
> [  297.425994]        dev_attr_store+0x3f/0x60
> [  297.425995]        sysfs_kf_write+0x89/0xb0
> [  297.425995]        kernfs_fop_write+0x188/0x240
> [  297.425996]        __vfs_write+0x50/0xa0
> [  297.425997]        vfs_write+0x105/0x290
> [  297.425997]        ksys_write+0xc6/0x160
> [  297.425998]        __x64_sys_write+0x43/0x50
> [  297.425999]        do_syscall_64+0xcc/0x76c
> [  297.426000]        entry_SYSCALL_64_after_hwframe+0x49/0xbe

I suppose you run with CONFIG_DEBUG_VM...

So we have

port->lock -> MM -> zone->lock
	// from pty_write()->__tty_buffer_request_room()->kmalloc()

vs

zone->lock -> printk() -> port->lock
	// from __offline_pages()->__offline_isolated_pages()->printk()

A number of debugging options make the kernel less stable.
Sad but true.

	-ss

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