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Subject: Re: linux hangs with printk on schedule()
From: Robert Love <rml@tech9.net>
To: Haoqiang Zheng <hzheng@cs.columbia.edu>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <05db01c2cbe5$4b4c34f0$9c2a3b80@zhengthinkpad>
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On Mon, 2003-02-03 at 19:35, Haoqiang Zheng wrote:

> I found Linux hangs when printk is inserted to the function schedule().
> Sure, it doesn't make much sense to add such a line to schedule(). But Linux
> shouldn't hang anyway, right? It's assumed that printk can be inserted
> safely to anywhere. So, is it a bug of Linux?

Its a known deadlock in 2.4:

	schedule -> printk() -> dmesg output -> klogd wakes up -> repeat

It is not a hard fix and its basically one of a few places where you
cannot call printk(), which is otherwise a very robust funciton.

	Robert Love

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