linux-kernel - Re: [PATCH v16 4/4] trace,x86: Add irq vector tracepoints

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Date:	Wed, 19 Jun 2013 16:56:30 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Seiji Aguchi <seiji.aguchi@....com>
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...e.hu, bp@...en8.de, linux-edac@...r.kernel.org,
	tony.luck@...el.com, tomoki.sekiyama@....com,
	dle-develop@...ts.sourceforge.net
Subject: Re: [PATCH v16 4/4] trace,x86: Add irq vector tracepoints

The function tracer self test would crash hard after applying this
patch. I found the bug:



On Tue, 2013-06-18 at 15:01 -0400, Seiji Aguchi wrote:
>  /*
>   * the load_current_idt() is called with interrupt disabled by
> local_irq_save()
>   * to avoid races. That way the IDT will always be set back to the
> expected
> @@ -442,6 +508,8 @@ static inline void load_current_idt(void)
>         local_irq_save(flags);
>         if (is_debug_idt_enabled())
>                 load_debug_idt();
> +       if (is_trace_idt_enabled())
> +               load_trace_idt();

This should be:

	else if (is_trace_idt_enabled())

Otherwise, you just totally negated the previous if.

-- Steve

>         else
>                 load_idt((const struct desc_ptr *)&idt_descr);
>         local_irq_restore(flags); 

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