linux-kernel - Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive cycle in spin

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56A819A4.3080702@hurleysoftware.com>
Date:	Tue, 26 Jan 2016 17:13:08 -0800
From:	Peter Hurley <peter@...leysoftware.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Byungchul Park <byungchul.park@....com>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	akinobu.mita@...il.com, jack@...e.cz, torvalds@...ux-foundation.org
Subject: Re: [PATCH v2] lib/spinlock_debug.c: prevent an infinite recursive
 cycle in spin_dump()

On 01/26/2016 04:11 PM, Andrew Morton wrote:
> On Mon, 18 Jan 2016 09:58:12 +0900 Byungchul Park <byungchul.park@....com> wrote:
> 
>> It causes an infinite recursive cycle when using CONFIG_DEBUG_SPINLOCK,
>> in the spin_dump(). Backtrace prints printk() -> console_trylock() ->
>> do_raw_spin_lock() -> spint_bug() -> spin_dump() -> printk()...
>> infinitely.
>>
>> If the spin_bug() is called from a function like printk() which is
>> trying to obtain the console lock, we should prevent the debug spinlock
>> code from calling printk() again in that context.
>>
> 
> lol.  Excellent.

[...]

> I can't immediately think of anything better than this.  It's a hack, but
> it's a small and quite clear hack.

Andrew,

I think you may have missed this follow-up from Byungchul:

On 01/21/2016 12:12 AM, Byungchul Park wrote:
> I was careless. I think it should be fixed by another way, instead of
> the way this patch suggested.

Regards,
Peter Hurley