[BUG] rockpro64 board hangs in console_init() after commit 10e14073107d

[Petr Mladek]

On Tue 2022-06-14 14:23:42, Alexandru Elisei wrote:
> With this change:
> 
> diff --git a/init/main.c b/init/main.c
> index 0ee39cdcfcac..a245982eb8a2 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1057,6 +1057,8 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
> 
>         kmem_cache_init_late();
> 
> +       lockdep_init();
> +
>         /*
>          * HACK ALERT! This is early. We're enabling the console before
>          * we've done PCI setups etc, and console_init() must be aware of
> @@ -1067,8 +1069,6 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
>                 panic("Too many boot %s vars at `%s'", panic_later,
>                       panic_param);
> 
> -       lockdep_init();
> -
>         /*
>          * Need to run this when irqs are enabled, because it wants
>          * to self-test [hard/soft]-irqs on/off lock inversion bugs
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index ea3dd55709e7..aa7684c6745d 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2705,7 +2705,10 @@ static int console_cpu_notify(unsigned int cpu)
>   */
>  void console_lock(void)
>  {
> +       pr_info("before might_sleep()");
>         might_sleep();
> +       pr_info("before down_console_sem()");
> +       pr_info("before down_console_sem()");
> 
>         down_console_sem();
>         if (console_suspended)
> @@ -3508,12 +3511,18 @@ int unregister_console(struct console *console)
>         if (console->exit)
>                 res = console->exit(console);
> 
> +       pr_info("Exiting from unregister_console(), res = %d", res);
> +       pr_info("Exiting from unregister_console(), res = %d", res);
> +
>         return res;
> 
>  out_disable_unlock:
>         console->flags &= ~CON_ENABLED;
>         console_unlock();
> 
> +       pr_info("Exiting from unregister_console(), res = %d", res);
> +       pr_info("Exiting from unregister_console(), res = %d", res);
> +
>         return res;
>  }
>  EXPORT_SYMBOL(unregister_console);
> 
> Some of the pr_info statements are duplicated to see the output just before
> the console hangs (I assume they're needed to force a buffer flush).
> 
> This is what I got:
> 
> [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd034]
> [    0.000000] Linux version 5.19.0-rc2-dirty (alex at monolith) (aarch64-linux-gnu-gcc (GCC) 12.1.0, GNU ld (GNU Binutils) 2.38) #106 SMP PREEMPT Tue Jun 14 14:03:30 BST 2022
> [    0.000000] Machine model: Pine64 RockPro64 v2.0
> [    0.000000] efi: UEFI not found.
> [    0.000000] earlycon: uart0 at MMIO32 0x00000000ff1a0000 (options '1500000n8')
> [    0.000000] printk: before might_sleep()
> [    0.000000] printk: before down_console_sem()
> [    0.000000] printk: before down_console_sem()
> [    0.000000] printk: bootconsole [uart0] enabled
> [    0.000000] NUMA: No NUMA configuration found
> [    0.000000] NUMA: Faking a node at [mem 0x0000000000200000-0x00000000f7ffffff]
> [    0.000000] NUMA: NODE_DATA [mem 0xf77cef40-0xf77d0fff]
[...]
> [    0.000001] sched_clock: 56 bits at 24MHz, resolution 41ns, wraps every 4398046511097ns
> [    0.005602] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
> [    0.006373] ... MAX_LOCKDEP_SUBCLASSES:  8
> [    0.006789] ... MAX_LOCK_DEPTH:          48
> [    0.007212] ... MAX_LOCKDEP_KEYS:        8192
> [    0.007651] ... CLASSHASH_SIZE:          4096
> [    0.008088] ... MAX_LOCKDEP_ENTRIES:     32768
> [    0.008535] ... MAX_LOCKDEP_CHAINS:      65536
> [    0.008981] ... CHAINHASH_SIZE:          32768
> [    0.009428]  memory used by lock dependency info: 6365 kB
> [    0.010018]  memory used for stack traces: 4224 kB
> [    0.010500]  per task-struct memory footprint: 1920 bytes
> [    0.011059] printk: before might_sleep()
> [    0.011079] printk: before down_console_sem()
> [    0.011477] printk: before down_console_sem()
> [    0.012112] Console: colour dummy device 80x25
> [    0.012984] printk: before might_sleep()
> [    0.013003] printk: before down_console_sem()
> [    0.013399] printk: before down_console_sem()
> [    0.013860] printk: console [tty0] enabled
> [    0.014986] printk: bootconsole [uart0] disabled
> [    0.015564] printk: before might_sleep()
> [    0.015582] printk: before down_console_sem()

I think that it did not print the 2nd "printk: before
down_console_sem()" because there was missing newline "\n".

printk() keeps such a line open because pr_cont() might append
to it. The message will get printed to the console only when
pr_cont("bla bla \n") is called or when another non-continuous
printk() is called.

> > Does the system boot when you avoid "earlycon" parameter?
> 
> It doesn't boot, it hangs and I don't get any output.

The difference might be that earlycon uses the serial port.
While the normal console is terminal "tty0".

Does it help to configure also the normal serial console.
I mean booting with something like:

earlycon console=uart,mmio32,0x00000000ff1a0000,1500000n8 console=tty0

I am not completely sure about the console=uart parameter. It is a
shame but I have never used it. I took the format from
Documentation/admin-guide/kernel-parameters.txt and the values
from your boot log:

[    0.000000] earlycon: uart0 at MMIO32 0x00000000ff1a0000 (options '1500000n8')

> > > I've booted a kernel compiled with CONFIG_PROVE_LOCKING=y, as the offending
> > > commit fiddles with locks, but no splat was produced that would explain the
> > > hang. I've also tried to boot a v5,19-rc2 kernel on my odroid-c4, the board
> > > is booting just fine, so I'm guessing it only affects of subset of arm64
> > > boards.
> > 
> > You might try to switch the order of console_init() and lockdep_init()
> > in start_kernel() in init/main.c
> 
> Did so above.

Unfortunately, it did not print anything :-(

Best Regards,
Petr