linux-kernel - Re: [PATCH] ftrace: handle archs that do not support irqs_disabled

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Date:	Tue, 28 Oct 2008 17:25:21 +1000
From:	Greg Ungerer <gerg@...pgear.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Richard Henderson <rth@...ddle.net>,
	Greg Ungerer <gerg@...inux.org>,
	Linux/m68k <linux-m68k@...r.kernel.org>,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] ftrace: handle archs that do not support irqs_disabled_flags

Hi Geert,

Geert Uytterhoeven wrote:
> On Fri, 24 Oct 2008, Steven Rostedt wrote:
>> Some architectures do not support a way to read the irq flags that
>> is set from "local_irq_save(flags)" to determine if interrupts were
>> disabled or enabled. Ftrace uses this information to display to the user
>> if the trace occurred with interrupts enabled or disabled.
> 
> Both alpha
> 
> 	#define irqs_disabled() (getipl() == IPL_MAX)
> 
> and m68k
> 
> 	static inline int irqs_disabled(void)
> 	{
> 		unsigned long flags;
> 		local_save_flags(flags);
> 		return flags & ~ALLOWINT;
> 	}
> 
> do have irqs_disabled(), but they don't have irqs_disabled_flags().
> 
> M68knommu has both, but they don't check the same thing:
> 
> 	#define irqs_disabled()                 \
> 	({                                      \
> 		unsigned long flags;            \
> 		local_save_flags(flags);        \
> 		((flags & 0x0700) == 0x0700);   \
> 	})
> 
> 	static inline int irqs_disabled_flags(unsigned long flags)
> 	{
> 		if (flags & 0x0700)
> 			return 0;
> 		else
> 			return 1;
> 	}
> 
> Is there a semantic difference between them (except that the latter takes the
> flags as a parameter)?

No...


> Or can we just extract the core logic of irqs_disabled() into
> irqs_disabled_flags()?

Yep, could certainly do that. I'll put a patch together.

Regards
Greg



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Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@...pgear.com
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