Re: arm64: pstore: printk causing hang during boot in __memcpy_toio with pstore enabled

[Guenter Roeck]

On 08/01/2018 05:35 AM, Ivid Suvarna wrote:
> Hi,
>
> When pstore is enabled and a *pr_info(any printk) in
> __memcpy_toio(arch/arm64/kernel/io.c)* is added, kernel wont boot and
> just hangs.
>
> The path where __memcpy_toio is called is below:
>
> ->persistent_ram_update
>    -> memcpy_toio
>      -> __memcpy_toio
>
> I tried with trace_printk and kernel boots fine. I understand that
> printk has overhead, but is this expected when we use some printk
> statement in __memcpy_toio?

I think the problem may be that the printk() output is copied to pstore.
Since pstore calls memcpy_toio(), you get a nice recursion if you add a
printk() call to it.

Guenter