linux-kernel - Re: [PATCH v2 3.18-rc3] kdb: Avoid printing KERN

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Date:	Fri, 07 Nov 2014 09:16:50 -0800
From:	Joe Perches <joe@...ches.com>
To:	Daniel Thompson <daniel.thompson@...aro.org>
Cc:	Jason Wessel <jason.wessel@...driver.com>,
	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, patches@...aro.org,
	linaro-kernel@...ts.linaro.org,
	John Stultz <john.stultz@...aro.org>,
	Sumit Semwal <sumit.semwal@...aro.org>, stable@...r.kernel.org
Subject: Re: [PATCH v2 3.18-rc3] kdb: Avoid printing KERN_ levels to consoles

On Fri, 2014-11-07 at 16:50 +0000, Daniel Thompson wrote:
> On 07/11/14 16:04, Joe Perches wrote:
> > why insert KERN_INFO?
> 
> vkdb_printf() and  printk() can appear either way round in a stack
> trace. Each is capable of calling the other and a flag (kdb_trap_printk)
> is used to prevent mutual recursion.

I see.

> A complete solution would require a means to know whether vkdb_printf()
> were entered directly or from printk(). A flag passed to vkdb_printf()
> would achieve this. I'll take a look.

That bit seems pretty simple and sensible.

I don't know this code at all but would it be better if
the kdb_trap_printk accesses were converted to atomic_<foo>?

Might this bit in vkdb_printf:

	saved_trap_printk = kdb_trap_printk;
	kdb_trap_printk = 0;

be better atomic_xchg?

and the kdb_trap_printk++ bits as atomic_inc, etc...

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