linux-kernel - Re: [PATCH 1/1] serial: 8250, disable "too much work" messages

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Message-ID: <20140402174342.1f78a39e@alan.etchedpixels.co.uk>
Date:	Wed, 2 Apr 2014 17:43:42 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] serial: 8250, disable "too much work" messages

> So, according to Takashi's measurements, we would need over 15000 loops
> on a single port. Of course, this value is highly dependent on a system.
> On my system, it is like 7 times lower (2100). And it lasts ~300ms here.
> 
> I suppose a limit like 32k loops is way too much and I just should go
> and implement the polling. Or what about adding inter-character sleeps
> to qemu to correspond to the speed? I can do that too, but I am not sure
> if limiting the throughput will be accepted by them.

The other option would be to detect qemu as a buggy uart, log a warning
and ignore the test on it. I think polling might be better, and that
would probably fix hang cases on real buggy uarts where right now we
sometimes keel over.

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