linux-kernel - Re: [2.6.25-rc5-mm1] BUG: spinlock bad magic early during boot

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Message-Id: <1205525184.12763.32.camel@nimitz.home.sr71.net>
Date:	Fri, 14 Mar 2008 13:06:24 -0700
From:	Dave Hansen <haveblue@...ibm.com>
To:	Tilman Schmidt <tilman@...p.cc>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Thomas Renninger <trenn@...e.de>,
	Eric Piel <eric.piel@...mplin-utc.net>,
	Len Brown <len.brown@...el.com>,
	Linus Torvalds <torvalds@...l.org>,
	Christoph Hellwig <hch@...radead.org>,
	Markus Gaugusch <dsdt@...gusch.at>, linux-acpi@...r.kernel.org
Subject: Re: [2.6.25-rc5-mm1] BUG: spinlock bad magic early during boot

For those of you new to this thread, here's the initial report:

	http://marc.info/?t=120536629300001&r=1&w=2

I'm pretty sure the root cause of this bug is this commit:

	ACPI: basic initramfs DSDT override support
	71fc47a9adf8ee89e5c96a47222915c5485ac437

Which did this hunk:

        @@ -648,6 +654,7 @@ asmlinkage void __init start_kernel(void)

                check_bugs();

        +       populate_rootfs(); /* For DSDT override from initramfs
        */
                acpi_early_init(); /* before LAPIC and SMP init */

                /* Do the rest non-__init'ed, we're now alive */
        	rest_init();
        ...

Well, the fs initcalls aren't actually done until during rest_init(),
including initializing my mnt_writer[] spinlocks.  I guess I could
statically initialize them, but that's not the root of the problem, it's
just the canary in the coal mine.

I think the populate_rootfs() call is completely bogus and certainly
can't be done before the initcalls.  But, I don't immediately have any
better suggestions for you.  Can you delay the ACPI init until after the
fs initcalls are made?

-- Dave

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