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xen-devel
[Xen-devel] Re: [patch] x86, paravirt-spinlocks: fix boot hang
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To: |
Ingo Molnar <mingo@xxxxxxx> |
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Subject: |
[Xen-devel] Re: [patch] x86, paravirt-spinlocks: fix boot hang |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Wed, 09 Jul 2008 08:55:43 -0700 |
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Cc: |
Jens Axboe <axboe@xxxxxxxxx>, Nick Piggin <nickpiggin@xxxxxxxxxxxx>, Xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>, Christoph Lameter <clameter@xxxxxxxxxxxxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Petr Tesarik <ptesarik@xxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxxxx>, Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Thomas Friebel <thomas.friebel@xxxxxxx> |
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Wed, 09 Jul 2008 08:56:38 -0700 |
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Ingo Molnar wrote:
* Ingo Molnar <mingo@xxxxxxx> wrote:
the patches caused a boot hang with this config:
http://redhat.com/~mingo/misc/config-Wed_Jul__9_14_47_04_CEST_2008.bad
ok, fixed it via the patch below.
Ingo
-------------->
commit 6412367fe22dc54cc727e7bec5bd65c36c1a0754
Author: Ingo Molnar <mingo@xxxxxxx>
Date: Wed Jul 9 15:42:09 2008 +0200
x86, paravirt-spinlocks: fix boot hang
the paravirt-spinlock patches caused a boot hang with this config:
http://redhat.com/~mingo/misc/config-Wed_Jul__9_14_47_04_CEST_2008.bad
i have bisected it down to:
| commit e17b58c2e85bc2ad2afc07fb8d898017c2b75ed1
| Author: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
| Date: Mon Jul 7 12:07:53 2008 -0700
|
| xen: implement Xen-specific spinlocks
i.e. applying that patch alone causes the hang. The hang happens in the
ftrace self-test:
initcall utsname_sysctl_init+0x0/0x19 returned 0 after 0 msecs
calling init_sched_switch_trace+0x0/0x4c
Testing tracer sched_switch: PASSED
initcall init_sched_switch_trace+0x0/0x4c returned 0 after 167 msecs
calling init_function_trace+0x0/0x12
Testing tracer ftrace:
[hard hang]
it should have continued like this:
Testing tracer ftrace: PASSED
initcall init_function_trace+0x0/0x12 returned 0 after 198 msecs
calling init_irqsoff_tracer+0x0/0x14
Testing tracer irqsoff: PASSED
initcall init_irqsoff_tracer+0x0/0x14 returned 0 after 3 msecs
calling init_mmio_trace+0x0/0x12
initcall init_mmio_trace+0x0/0x12 returned 0 after 0 msecs
the problem is that such lowlevel primitives as spinlocks should never
be built with -pg (which ftrace does). Marking paravirt.o as non-pg and
marking all spinlock ops as always-inline solve the hang.
Thanks Ingo, that would have taken me a while to work out.
Presumably that means that xen/smp.o should also be built without -pg.
In fact, should I move the spinlock code into its own file, so that
ftrace can cover as much as it can?
J
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