linux-kernel - Re: [PATCH 1/4] Blackfin: arch patch for 2.6.18

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Message-Id: <200609272257.02385.arnd@arndb.de>
Date:	Wed, 27 Sep 2006 22:57:02 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Robin Getz <rgetz@...ckfin.uclinux.org>
Cc:	luke Yang <luke.adi@...il.com>, Andrew Morton <akpm@...l.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] Blackfin: arch patch for 2.6.18

Am Wednesday 27 September 2006 19:19 schrieb Robin Getz:
> OK - I was just doing the similar thing to what already exists in
> ./asm-blackfin/system.h
>
> #define local_irq_enable() do {         \
>          __asm__ __volatile__ (          \
>                  "sti %0;"               \
>                  ::"d"(irq_flags));      \
> } while (0)
>
> which could be simplified to:
>
> #define local_irq_enable() __asm__ __volatile__ ("sti %0;"  ::"d"(irq_flags));

Actually, this one is slightly broken, because of the ';' at the end of the
macro (think of "if(x) local_irq_enable(); else somthing_else()").

What I was suggesting is to make a proper inline function, like

static inline void local_irq_enable(void)
{
	unsigned long unused_flags;
	asm volatile ("sti %0;" : : "d" (unused_flags));
}

That completely avoids all the problems you might hit with macro expansion,
while still compiling to the same code.

	Arnd <><
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