Cc-ing Ted, Arnd, Greg
On (09/10/19 11:22), Qian Cai wrote:
> [ 1078.283869][T43784] -> #3 (&(&port->lock)->rlock){-.-.}:
> [ 1078.291350][T43784] __lock_acquire+0x5c8/0xbb0
> [ 1078.296394][T43784] lock_acquire+0x154/0x428
> [ 1078.301266][T43784] _raw_spin_lock_irqsave+0x80/0xa0
> [ 1078.306831][T43784] tty_port_tty_get+0x28/0x68
> [ 1078.311873][T43784] tty_port_default_wakeup+0x20/0x40
> [ 1078.317523][T43784] tty_port_tty_wakeup+0x38/0x48
> [ 1078.322827][T43784] uart_write_wakeup+0x2c/0x50
> [ 1078.327956][T43784] pl011_tx_chars+0x240/0x260
> [ 1078.332999][T43784] pl011_start_tx+0x24/0xa8
> [ 1078.337868][T43784] __uart_start+0x90/0xa0
> [ 1078.342563][T43784] uart_write+0x15c/0x2c8
> [ 1078.347261][T43784] do_output_char+0x1c8/0x2b0
> [ 1078.352304][T43784] n_tty_write+0x300/0x668
> [ 1078.357087][T43784] tty_write+0x2e8/0x430
> [ 1078.361696][T43784] redirected_tty_write+0xcc/0xe8
> [ 1078.367086][T43784] do_iter_write+0x228/0x270
> [ 1078.372041][T43784] vfs_writev+0x10c/0x1c8
> [ 1078.376735][T43784] do_writev+0xdc/0x180
> [ 1078.381257][T43784] __arm64_sys_writev+0x50/0x60
> [ 1078.386476][T43784] el0_svc_handler+0x11c/0x1f0
> [ 1078.391606][T43784] el0_svc+0x8/0xc
> [ 1078.395691][T43784]
uart_port->lock -> tty_port->lock
This thing along is already a bit suspicious. We re-enter tty
here: tty -> uart -> serial -> tty
And we re-enter tty under uart_port->lock.
> [ 1078.395691][T43784] -> #2 (&port_lock_key){-.-.}:
> [ 1078.402561][T43784] __lock_acquire+0x5c8/0xbb0
> [ 1078.407604][T43784] lock_acquire+0x154/0x428
> [ 1078.412474][T43784] _raw_spin_lock+0x68/0x88
> [ 1078.417343][T43784] pl011_console_write+0x2ac/0x318
> [ 1078.422820][T43784] console_unlock+0x3c4/0x898
> [ 1078.427863][T43784] vprintk_emit+0x2d4/0x460
> [ 1078.432732][T43784] vprintk_default+0x48/0x58
> [ 1078.437688][T43784] vprintk_func+0x194/0x250
> [ 1078.442557][T43784] printk+0xbc/0xec
> [ 1078.446732][T43784] register_console+0x4a8/0x580
> [ 1078.451947][T43784] uart_add_one_port+0x748/0x878
> [ 1078.457250][T43784] pl011_register_port+0x98/0x128
> [ 1078.462639][T43784] sbsa_uart_probe+0x398/0x480
> [ 1078.467772][T43784] platform_drv_probe+0x70/0x108
> [ 1078.473075][T43784] really_probe+0x15c/0x5d8
> [ 1078.477944][T43784] driver_probe_device+0x94/0x1d0
> [ 1078.483335][T43784] __device_attach_driver+0x11c/0x1a8
> [ 1078.489072][T43784] bus_for_each_drv+0xf8/0x158
> [ 1078.494201][T43784] __device_attach+0x164/0x240
> [ 1078.499331][T43784] device_initial_probe+0x24/0x30
> [ 1078.504721][T43784] bus_probe_device+0xf0/0x100
> [ 1078.509850][T43784] device_add+0x63c/0x960
> [ 1078.514546][T43784] platform_device_add+0x1ac/0x3b8
> [ 1078.520023][T43784] platform_device_register_full+0x1fc/0x290
> [ 1078.526373][T43784] acpi_create_platform_device.part.0+0x264/0x3a8
> [ 1078.533152][T43784] acpi_create_platform_device+0x68/0x80
> [ 1078.539150][T43784] acpi_default_enumeration+0x34/0x78
> [ 1078.544887][T43784] acpi_bus_attach+0x340/0x3b8
> [ 1078.550015][T43784] acpi_bus_attach+0xf8/0x3b8
> [ 1078.555057][T43784] acpi_bus_attach+0xf8/0x3b8
> [ 1078.560099][T43784] acpi_bus_attach+0xf8/0x3b8
> [ 1078.565142][T43784] acpi_bus_scan+0x9c/0x100
> [ 1078.570015][T43784] acpi_scan_init+0x16c/0x320
> [ 1078.575058][T43784] acpi_init+0x330/0x3b8
> [ 1078.579666][T43784] do_one_initcall+0x158/0x7ec
> [ 1078.584797][T43784] kernel_init_freeable+0x9a8/0xa70
> [ 1078.590360][T43784] kernel_init+0x18/0x138
> [ 1078.595055][T43784] ret_from_fork+0x10/0x1c
>
> [ 1078.599835][T43784] -> #1 (console_owner){-...}:
> [ 1078.606618][T43784] __lock_acquire+0x5c8/0xbb0
> [ 1078.611661][T43784] lock_acquire+0x154/0x428
> [ 1078.616530][T43784] console_unlock+0x298/0x898
> [ 1078.621573][T43784] vprintk_emit+0x2d4/0x460
> [ 1078.626442][T43784] vprintk_default+0x48/0x58
> [ 1078.631398][T43784] vprintk_func+0x194/0x250
> [ 1078.636267][T43784] printk+0xbc/0xec
> [ 1078.640443][T43784] _warn_unseeded_randomness+0xb4/0xd0
> [ 1078.646267][T43784] get_random_u64+0x4c/0x100
> [ 1078.651224][T43784] add_to_free_area_random+0x168/0x1a0
> [ 1078.657047][T43784] free_one_page+0x3dc/0xd08
> [ 1078.662003][T43784] __free_pages_ok+0x490/0xd00
> [ 1078.667132][T43784] __free_pages+0xc4/0x118
> [ 1078.671914][T43784] __free_pages_core+0x2e8/0x428
> [ 1078.677219][T43784] memblock_free_pages+0xa4/0xec
> [ 1078.682522][T43784] memblock_free_all+0x264/0x330
> [ 1078.687825][T43784] mem_init+0x90/0x148
> [ 1078.692259][T43784] start_kernel+0x368/0x684
zone->lock --> uart_port->lock
Some debugging options/warnings/error print outs/etc introduce
deadlock patterns.
This adds zone->lock --> uart_port->lock, which then brings in
uart_port->lock --> tty_port->lock, which in turn brings
tty_port->lock --> zone->lock.
> [ 1078.697126][T43784] -> #0 (&(&zone->lock)->rlock){-.-.}:
> [ 1078.704604][T43784] check_prev_add+0x120/0x1138
> [ 1078.709733][T43784] validate_chain+0x888/0x1270
> [ 1078.714863][T43784] __lock_acquire+0x5c8/0xbb0
> [ 1078.719906][T43784] lock_acquire+0x154/0x428
> [ 1078.724776][T43784] _raw_spin_lock+0x68/0x88
> [ 1078.729645][T43784] rmqueue_bulk.constprop.21+0xb0/0x1218
> [ 1078.735643][T43784] get_page_from_freelist+0x898/0x24a0
> [ 1078.741467][T43784] __alloc_pages_nodemask+0x2a8/0x1d08
> [ 1078.747291][T43784] alloc_pages_current+0xb4/0x150
> [ 1078.752682][T43784] allocate_slab+0xab8/0x2350
> [ 1078.757725][T43784] new_slab+0x98/0xc0
> [ 1078.762073][T43784] ___slab_alloc+0x66c/0xa30
> [ 1078.767029][T43784] __slab_alloc+0x68/0xc8
> [ 1078.771725][T43784] __kmalloc+0x3d4/0x658
> [ 1078.776333][T43784] __tty_buffer_request_room+0xd4/0x220
> [ 1078.782244][T43784] tty_insert_flip_string_fixed_flag+0x6c/0x128
> [ 1078.788849][T43784] pty_write+0x98/0x100
> [ 1078.793370][T43784] n_tty_write+0x2a0/0x668
> [ 1078.798152][T43784] tty_write+0x2e8/0x430
> [ 1078.802760][T43784] __vfs_write+0x5c/0xb0
> [ 1078.807368][T43784] vfs_write+0xf0/0x230
> [ 1078.811890][T43784] ksys_write+0xd4/0x180
> [ 1078.816498][T43784] __arm64_sys_write+0x4c/0x60
> [ 1078.821627][T43784] el0_svc_handler+0x11c/0x1f0
> [ 1078.826756][T43784] el0_svc+0x8/0xc
tty_port->lock --> zone->lock
> [ 1078.830842][T43784] other info that might help us debug this:
> [ 1078.830842][T43784]
> [ 1078.840918][T43784] Chain exists of:
> [ 1078.840918][T43784] &(&zone->lock)->rlock --> &port_lock_key --> &(&port-> >lock)->rlock
> [ 1078.840918][T43784]
> [ 1078.854731][T43784] Possible unsafe locking scenario:
> [ 1078.854731][T43784]
> [ 1078.862029][T43784] CPU0 CPU1
> [ 1078.867243][T43784] ---- ----
> [ 1078.872457][T43784] lock(&(&port->lock)->rlock);
> [ 1078.877238][T43784] lock(&port_lock_key);
> [ 1078.883929][T43784] lock(&(&port->lock)->rlock);
> [ 1078.891228][T43784] lock(&(&zone->lock)->rlock);
> [ 1078.896010][T43784]
> [ 1078.896010][T43784] *** DEADLOCK ***
[..]
> [ 1078.980932][T43784] dump_backtrace+0x0/0x228
> [ 1078.985279][T43784] show_stack+0x24/0x30
> [ 1078.989282][T43784] dump_stack+0xe8/0x13c
> [ 1078.993370][T43784] print_circular_bug+0x334/0x3d8
> [ 1078.998240][T43784] check_noncircular+0x268/0x310
> [ 1079.003022][T43784] check_prev_add+0x120/0x1138
> [ 1079.007631][T43784] validate_chain+0x888/0x1270
> [ 1079.012241][T43784] __lock_acquire+0x5c8/0xbb0
> [ 1079.016763][T43784] lock_acquire+0x154/0x428
> [ 1079.021111][T43784] _raw_spin_lock+0x68/0x88
> [ 1079.025460][T43784] rmqueue_bulk.constprop.21+0xb0/0x1218
> [ 1079.030937][T43784] get_page_from_freelist+0x898/0x24a0
> [ 1079.036240][T43784] __alloc_pages_nodemask+0x2a8/0x1d08
> [ 1079.041542][T43784] alloc_pages_current+0xb4/0x150
> [ 1079.046412][T43784] allocate_slab+0xab8/0x2350
> [ 1079.050934][T43784] new_slab+0x98/0xc0
> [ 1079.054761][T43784] ___slab_alloc+0x66c/0xa30
> [ 1079.059196][T43784] __slab_alloc+0x68/0xc8
> [ 1079.063371][T43784] __kmalloc+0x3d4/0x658
> [ 1079.067458][T43784] __tty_buffer_request_room+0xd4/0x220
> [ 1079.072847][T43784] tty_insert_flip_string_fixed_flag+0x6c/0x128
> [ 1079.078932][T43784] pty_write+0x98/0x100
> [ 1079.082932][T43784] n_tty_write+0x2a0/0x668
> [ 1079.087193][T43784] tty_write+0x2e8/0x430
> [ 1079.091280][T43784] __vfs_write+0x5c/0xb0
> [ 1079.095367][T43784] vfs_write+0xf0/0x230
> [ 1079.099368][T43784] ksys_write+0xd4/0x180
> [ 1079.103455][T43784] __arm64_sys_write+0x4c/0x60
> [ 1079.108064][T43784] el0_svc_handler+0x11c/0x1f0
> [ 1079.112672][T43784] el0_svc+0x8/0xc
tty_port->lock --> zone->lock
For instance, I don't really like the re-entrant tty, at least not
under uart_port->lock. This, maybe, can be one of the solutions.
Another one, a quick and dirty one, (and so many people will blame
me for this) would be to break zone->{printk}->uart chain...
Something like this
---
drivers/char/random.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 9b54cdb301d3..975015857200 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1687,8 +1687,9 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
print_once = true;
#endif
if (__ratelimit(&unseeded_warning))
- pr_notice("random: %s called from %pS with crng_init=%d\n",
- func_name, caller, crng_init);
+ printk_deferred(KERN_NOTICE "random: %s called from %pS "
+ "with crng_init=%d\n", func_name, caller,
+ crng_init);
}
/*
@@ -2462,4 +2463,4 @@ void add_bootloader_randomness(const void *buf, unsigned int size)
else
add_device_randomness(buf, size);
}
-EXPORT_SYMBOL_GPL(add_bootloader_randomness);
\ No newline at end of file
+EXPORT_SYMBOL_GPL(add_bootloader_randomness);
