linux-kernel - Re: Strange hang on ia64 with CONFIG_PRINTK

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Message-ID: <12c511ca0802131933g6aaaec9cidbfbfcac6f394c63@mail.gmail.com>
Date:	Wed, 13 Feb 2008 19:33:42 -0800
From:	"Tony Luck" <tony.luck@...el.com>
To:	"David Miller" <davem@...emloft.net>
Cc:	mingo@...e.hu, rdreier@...co.com, linux-kernel@...r.kernel.org
Subject: Re: Strange hang on ia64 with CONFIG_PRINTK_TIME=y

> That's right.  I thought you guys had something that would handle that
> early on, but looking at how the trick works in the vmlinux.lds.S ia64
> uses that isn't the case.

We try to get things set up pertty early ... but I agree this is
fragile.  Adding code to printk() to not provide a timestamp
before some safe point in boot is a workaround to the
current problem.  But it may come back to haunt us if
other per-cpu data is added that needs to be accessed
early during boot.

There are some changes going on at the moment on how
we allocate the space for the per-cpu area.  It is likely that
for a non-boot cpu we might be able to get everything that
we need for per-cpu access to work done in head.S before
we can get to any C code.  Boot cpu may be harder unless
we statically allocate space for its per-cpu area in
vmlinux.lds.S

I'll take a closer look at what is needed tomorrow.

-Tony
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