linux-kernel - Re: [PATCH 3/3] WorkStruct: Use direct assignment rather than cmpxchg()

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Message-ID: <26012.1165535903@redhat.com>
Date:	Thu, 07 Dec 2006 23:58:23 +0000
From:	David Howells <dhowells@...hat.com>
To:	Russell King <rmk+lkml@....linux.org.uk>
Cc:	David Howells <dhowells@...hat.com>, Andrew Morton <akpm@...l.org>,
	torvalds@...l.org, davem@...emloft.com, wli@...omorphy.com,
	matthew@....cx, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 3/3] WorkStruct: Use direct assignment rather than cmpxchg() 

Russell King <rmk+lkml@....linux.org.uk> wrote:

> Incorrect.  pre-v6 ARM bitops for test_and_xxx_bit() all do:
> 
> 	save and disable irqs
> 	load value
> 	test bit
> 	if not in desired state, alter bit and write it back
> 	restore irqs

Hmmm...  ARM has two implementations.  One in the header files which is what I
consulted when writing that email:

static inline void ____atomic_set_bit(unsigned int bit, volatile unsigned long *p)
{
	unsigned long flags;
	unsigned long mask = 1UL << (bit & 31);

	p += bit >> 5;

	raw_local_irq_save(flags);
	*p |= mask;
	raw_local_irq_restore(flags);
}

And the other in the libs which does as you say.  Why the one in the header
file at all?

David
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