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Date: Tue, 12 Dec 2017 15:51:05 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: Ingo Molnar <mingo@kernel.org>,
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        Karol Herbst <karolherbst@gmail.com>
Subject: Re: [tip:x86/urgent] x86/mm/kmmio: Fix mmiotrace for page unaligned
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On Tue, Dec 12, 2017 at 09:47:05AM -0500, Ilia Mirkin wrote:
> > So this 'thing' has huge gaping SMP holes in.
> 
> Sure does! Probably why the following happens when mmiotrace is enabled:
> 
> void enable_mmiotrace(void)
> {
>         mutex_lock(&mmiotrace_mutex);
>         if (is_enabled())
>                 goto out;
> 
>         if (nommiotrace)
>                 pr_info("MMIO tracing disabled.\n");
>         kmmio_init();
>         enter_uniprocessor();

	^^^^^

Ah! I completely missed that. OK, that makes it much less broken :-)

If I don't forget, I'll add some comments to this file to clarify that.

Thanks!

>         spin_lock_irq(&trace_lock);
>         atomic_inc(&mmiotrace_enabled);
>         spin_unlock_irq(&trace_lock);
>         pr_info("enabled.\n");
> out:
>         mutex_unlock(&mmiotrace_mutex);
> }