> On Oct 5, 2019, at 7:29 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
>> -> #2 (&(&zone->lock)->rlock){-.-.}:
>> lock_acquire+0x21a/0x468
>> _raw_spin_lock+0x54/0x68
>> get_page_from_freelist+0x8b6/0x2d28
>> __alloc_pages_nodemask+0x246/0x658
>> __get_free_pages+0x34/0x78
>> sclp_init+0x106/0x690
>> sclp_register+0x2e/0x248
>> sclp_rw_init+0x4a/0x70
>> sclp_console_init+0x4a/0x1b8
>> console_init+0x2c8/0x410
>> start_kernel+0x530/0x6a0
>> startup_continue+0x70/0xd0
>
> This appears to be the core of our problem?
There are more.
[ 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
[ 297.426001] other info that might help us debug this:
[ 297.426002] Chain exists of:
[ 297.426002] console_owner --> &(&port->lock)->rlock --> &(&zone->lock)-
>rlock
[ 297.426007] Possible unsafe locking scenario:
[ 297.426008] CPU0 CPU1
[ 297.426009] ---- ----
[ 297.426009] lock(&(&zone->lock)->rlock);
[ 297.426011] lock(&(&port->lock)->rlock);
[ 297.426013] lock(&(&zone->lock)->rlock);
[ 297.426014] lock(console_owner);
[ 297.426016] *** DEADLOCK ***
[ 297.426017] 9 locks held by test.sh/8653:
[ 297.426018] #0: ffff88839ba7d408 (sb_writers#4){.+.+}, at:
vfs_write+0x25f/0x290
[ 297.426021] #1: ffff888277618880 (&of->mutex){+.+.}, at:
kernfs_fop_write+0x128/0x240
[ 297.426024] #2: ffff8898131fc218 (kn->count#115){.+.+}, at:
kernfs_fop_write+0x138/0x240
[ 297.426028] #3: ffffffff86962a80 (device_hotplug_lock){+.+.}, at:
lock_device_hotplug_sysfs+0x16/0x50
[ 297.426031] #4: ffff8884374f4990 (&dev->mutex){....}, at:
device_offline+0x70/0x110
[ 297.426034] #5: ffffffff86515250 (cpu_hotplug_lock.rw_sem){++++}, at:
__offline_pages+0xbf/0xa10
[ 297.426037] #6: ffffffff867405f0 (mem_hotplug_lock.rw_sem){++++}, at:
percpu_down_write+0x87/0x2f0
[ 297.426040] #7: ffff88883fff3c58 (&(&zone->lock)->rlock){-.-.}, at:
__offline_isolated_pages+0x179/0x3e0
[ 297.426043] #8: ffffffff865a4920 (console_lock){+.+.}, at:
vprintk_emit+0x100/0x340
[ 297.426047] stack backtrace:
[ 297.426048] CPU: 1 PID: 8653 Comm: test.sh Not tainted 5.3.0-next-20190917 #8
[ 297.426049] Hardware name: HPE ProLiant DL560 Gen10/ProLiant DL560 Gen10,
BIOS U34 05/21/2019
[ 297.426049] Call Trace:
[ 297.426050] dump_stack+0x86/0xca
[ 297.426051] print_circular_bug.cold.31+0x243/0x26e
[ 297.426051] check_noncircular+0x29e/0x2e0
[ 297.426052] ? stack_trace_save+0x87/0xb0
[ 297.426053] ? print_circular_bug+0x120/0x120
[ 297.426053] check_prev_add+0x107/0xea0
[ 297.426054] validate_chain+0x8fc/0x1200
[ 297.426055] ? check_prev_add+0xea0/0xea0
[ 297.426055] __lock_acquire+0x5b3/0xb40
[ 297.426056] lock_acquire+0x126/0x280
[ 297.426057] ? console_unlock+0x207/0x750
[ 297.426057] ? __kasan_check_read+0x11/0x20
[ 297.426058] console_unlock+0x269/0x750
[ 297.426059] ? console_unlock+0x207/0x750
[ 297.426059] vprintk_emit+0x10d/0x340
[ 297.426060] vprintk_default+0x1f/0x30
[ 297.426061] vprintk_func+0x44/0xd4
[ 297.426061] ? do_raw_spin_lock+0x118/0x1d0
[ 297.426062] printk+0x9f/0xc5
[ 297.426063] ? kmsg_dump_rewind_nolock+0x64/0x64
[ 297.426064] ? __offline_isolated_pages+0x179/0x3e0
[ 297.426064] __offline_isolated_pages.cold.52+0x2f/0x30a
[ 297.426065] ? online_memory_block+0x20/0x20
[ 297.426066] offline_isolated_pages_cb+0x17/0x30
[ 297.426067] walk_system_ram_range+0xda/0x160
[ 297.426067] ? walk_mem_res+0x30/0x30
[ 297.426068] ? dissolve_free_huge_page+0x1e/0x2b0
[ 297.426069] __offline_pages+0x79c/0xa10
[ 297.426069] ? __add_memory+0xc0/0xc0
[ 297.426070] ? __kasan_check_write+0x14/0x20
[ 297.426071] ? __mutex_lock+0x344/0xcd0
[ 297.426071] ? _raw_spin_unlock_irqrestore+0x49/0x50
[ 297.426072] ? device_offline+0x70/0x110
[ 297.426073] ? klist_next+0x1c1/0x1e0
[ 297.426073] ? __mutex_add_waiter+0xc0/0xc0
[ 297.426074] ? klist_next+0x10b/0x1e0
[ 297.426075] ? klist_iter_exit+0x16/0x40
[ 297.426076] ? device_for_each_child+0xd0/0x110
[ 297.426076] offline_pages+0x11/0x20
[ 297.426077] memory_subsys_offline+0x7e/0xc0
[ 297.426078] device_offline+0xd5/0x110
[ 297.426078] ? auto_online_blocks_show+0x70/0x70
[ 297.426079] state_store+0xc6/0xe0
[ 297.426080] dev_attr_store+0x3f/0x60
[ 297.426080] ? device_match_name+0x40/0x40
[ 297.426081] sysfs_kf_write+0x89/0xb0
[ 297.426082] ? sysfs_file_ops+0xa0/0xa0
[ 297.426082] kernfs_fop_write+0x188/0x240
[ 297.426083] __vfs_write+0x50/0xa0
[ 297.426084] vfs_write+0x105/0x290
[ 297.426084] ksys_write+0xc6/0x160
[ 297.426085] ? __x64_sys_read+0x50/0x50
[ 297.426086] ? do_syscall_64+0x79/0x76c
[ 297.426086] ? do_syscall_64+0x79/0x76c
[ 297.426087] __x64_sys_write+0x43/0x50
[ 297.426088] do_syscall_64+0xcc/0x76c
[ 297.426088] ? trace_hardirqs_on_thunk+0x1a/0x20
[ 297.426089] ? syscall_return_slowpath+0x210/0x210
[ 297.426090] ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe
[ 297.426091] ? trace_hardirqs_off_caller+0x3a/0x150
[ 297.426092] ? trace_hardirqs_off_thunk+0x1a/0x20
[ 297.426092] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 297.426093] RIP: 0033:0x7fd7336b4e18
[ 297.426095] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00 f3 0f
1e fa 48 8d 05 05 59 2d 00 8b 00 85 c0 75 17 b8 01 00 00 00 0f 05 <48> 3d 00 f0
ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 d4 55
[ 297.426096] RSP: 002b:00007ffc58c7b258 EFLAGS: 00000246 ORIG_RAX:
0000000000000001
[ 297.426098] RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00007fd7336b4e18
[ 297.426098] RDX: 0000000000000008 RSI: 000055ad6d519c70 RDI: 0000000000000001
[ 297.426099] RBP: 000055ad6d519c70 R08: 000000000000000a R09: 00007fd733746300
[ 297.426100] R10: 000000000000000a R11: 0000000000000246 R12: 00007fd733986780
[ 297.426101] R13: 0000000000000008 R14: 00007fd733981740 R15: 0000000000000008
> At initialization time,
> the sclp driver registers an inappropriate dependency with lockdep. It
> does this by calling into the page allocator while holding sclp_lock.
> But we don't *want* to teach lockdep that sclp_lock nests outside
> zone->lock. We want the opposite.
>
> So can we address this class of problem by declaring "thou shalt not
> call the page allocator while holding a lock which can be taken on the
> prink path?". And then declare sclp to be defective.
>
>
> And I think sclp is kinda buggy-but-lucky anyway: if console output is
> directed to sclp device #0 and we're then trying to initialize sclp
> device #1 then any printk which happens during that initialization will
> deadlock. The driver escapes this by only
printk() is such a beast that basically any lock taken after console_lock held like sclp_lock, port_lock, rq_lock or even indirectly like pi_lock as in below,
console_lock -> rq_lock -> pi_lock
would have a same problem where if another CPU take one of those locks in a different path and call printk() could trigger a deadlock.
[ 763.659221][ C6] -> #2 (&rq->lock){-.-.}:
[ 763.659222][ C6] __lock_acquire+0x44e/0x8c0
[ 763.659223][ C6] lock_acquire+0xc0/0x1c0
[ 763.659223][ C6] _raw_spin_lock+0x2f/0x40
[ 763.659223][ C6] task_fork_fair+0x37/0x150
[ 763.659224][ C6] sched_fork+0x126/0x230
[ 763.659224][ C6] copy_process+0xafc/0x1e90
[ 763.659224][ C6] _do_fork+0x89/0x720
[ 763.659225][ C6] kernel_thread+0x58/0x70
[ 763.659225][ C6] rest_init+0x28/0x302
[ 763.659225][ C6] arch_call_rest_init+0xe/0x1b
[ 763.659226][ C6] start_kernel+0x581/0x5a0
[ 763.659226][ C6] x86_64_start_reservations+0x24/0x26
[ 763.659227][ C6] x86_64_start_kernel+0xef/0xf6
[ 763.659227][ C6] secondary_startup_64+0xb6/0xc0
[ 763.659227][ C6]
[ 763.659227][ C6] -> #1 (&p->pi_lock){-.-.}:
[ 763.659229][ C6] __lock_acquire+0x44e/0x8c0
[ 763.659229][ C6] lock_acquire+0xc0/0x1c0
[ 763.659230][ C6] _raw_spin_lock_irqsave+0x3a/0x50
[ 763.659230][ C6] try_to_wake_up+0x5c/0xbc0
[ 763.659230][ C6] wake_up_process+0x15/0x20
[ 763.659231][ C6] __up+0x4a/0x50
[ 763.659231][ C6] up+0x45/0x50
[ 763.659231][ C6] __up_console_sem+0x37/0x60
[ 763.659232][ C6] console_unlock+0x357/0x600
[ 763.659232][ C6] vprintk_emit+0x101/0x320
[ 763.659232][ C6] vprintk_default+0x1f/0x30
[ 763.659233][ C6] vprintk_func+0x44/0xd4
[ 763.659233][ C6] printk+0x58/0x6f
[ 763.659234][ C6] do_exit+0xd73/0xd80
[ 763.659234][ C6] do_group_exit+0x41/0xd0
[ 763.659234][ C6] __x64_sys_exit_group+0x18/0x20
[ 763.659235][ C6] do_syscall_64+0x6d/0x488
[ 763.659235][ C6] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> supporting a single device
> system-wide but it's not a model which drivers should generally follow.
>
> (And if sclp will only ever support a single device system-wide, why
> the heck does it need to take sclp_lock() on the device initialization
> path??)
