linux-kernel - arm64: pstore: printk causing hang during boot in __memcpy

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Message-ID: <CABXF_AAVhadw=+rtcD-L06-zBTMb3v7C2QqvN-6vcx5w2T0sYg@mail.gmail.com>
Date:   Wed, 1 Aug 2018 18:05:29 +0530
From:   Ivid Suvarna <ivid.suvarna@...il.com>
To:     Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>,
        Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jason Baron <jbaron@...hat.com>
Cc:     Kernel development list <linux-kernel@...r.kernel.org>,
        Joe Perches <joe@...ches.com>, linux-arm-msm@...r.kernel.org
Subject: arm64: pstore: printk causing hang during boot in __memcpy_toio with
 pstore enabled

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?

Or is it some kind of bug? Tested on db410c.

Please let me know your opinion.

Thanks,