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Date: Wed, 9 Dec 2009 16:52:36 +0800
Message-ID: <3877989d0912090052v79fdce6aqb507639143b5d71e@mail.gmail.com>
Subject: Re: [RFC PATCH] Add TRACE_IRQFLAGS_SUPPORT, LOCKDEP_SUPPORT then 
	enable ftrace for ia64
From: Luming Yu <luming.yu@gmail.com>
To: Tony Luck <tony.luck@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Christoph Hellwig <hch@infradead.org>,
       LKML <linux-kernel@vger.kernel.org>,
       "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
       "Yu, Fenghua" <fenghua.yu@intel.com>,
       "Li, Shaohua" <shaohua.li@intel.com>
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On Wed, Dec 9, 2009 at 2:45 PM, Luming Yu <luming.yu@gmail.com> wrote:
>>
>> But let me try more on other ia64 boxes that I can get access.
>>
>> Stay tuned.
>
> I might have reproduced the problem on a HP ia64 system
> with -32 kernel as the following info. But -31 kernel with
> lockdep code enabled just works. ....debugging...

ah, I seem to have found the change in -32 against -31 that causes the trouble.

Commenting out the change make -32 Lockdep kernel boot.

Tony, please let me know whether you can reproduce..

kernel/lockdep.c
static int save_trace(struct stack_trace *trace)
{
        trace->nr_entries = 0;
        trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
        trace->entries = stack_trace + nr_stack_trace_entries;

        trace->skip = 3;

        save_stack_trace(trace);
#if 0

        /*
         * Some daft arches put -1 at the end to indicate its a full trace.
         *
         * <rant> this is buggy anyway, since it takes a whole extra entry so a
         * complete trace that maxes out the entries provided will be reported
         * as incomplete, friggin useless </rant>
         */
        if (trace->entries[trace->nr_entries-1] == ULONG_MAX)
                trace->nr_entries--;
#endif
--
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