linux-kernel - Re: IRQ off latency of printk is very high

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Message-ID: <20071026202831.GP17536@waste.org>
Date:	Fri, 26 Oct 2007 15:28:31 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Benny Amorsen <benny+usenet@...rsen.dk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: IRQ off latency of printk is very high

On Fri, Oct 26, 2007 at 02:57:18PM +0200, Benny Amorsen wrote:
> >>>>> "MM" == Matt Mackall <mpm@...enic.com> writes:
> 
> MM> Well there are things we can do, yes, but I'd be worried that
> MM> they've give up the deterministic behavior we rely on quite
> MM> heavily for debugging. If event A happens before event B, we must
> MM> see the message from A before the one from B, even if B happens in
> MM> irq context.
> 
> MM> And if event B is a hard lock up, we'd also like to be sure the
> MM> message for A actually gets out. If B happens in the interrupt
> MM> that comes in when we re-enable them, that won't happen.
> 
> I can see the concerns, but right now it all leads to disabling serial
> console for real-time servers. That is even less helpful for
> debugging.

That's not clear. No data is often better than false or misleading
data.

-- 
Mathematics is the supreme nostalgia of our time.
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