linux-kernel - Re: [PATCH] Export current_is

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Date:	Wed, 6 Dec 2006 09:53:41 -0800 (PST)
From:	Linus Torvalds <torvalds@...l.org>
To:	David Howells <dhowells@...hat.com>
cc:	Andrew Morton <akpm@...l.org>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Roland Dreier <rdreier@...co.com>,
	Andy Fleming <afleming@...escale.com>,
	Ben Collins <ben.collins@...ntu.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jeff Garzik <jeff@...zik.org>
Subject: Re: [PATCH] Export current_is_keventd() for libphy 



On Wed, 6 Dec 2006, David Howells wrote:
> 
> +	if (get_wq_data(work) == cwq
> +	    && test_bit(WORK_STRUCT_PENDING, &work->management)
> 
> I wonder if those can be combined, perhaps:

Gcc should do it for us, afaik. I didn't check, but gcc is generally 
pretty good at combining logical operations like this, because it's very 
common.

> Otherwise for i386 the compiler can't combine them because test_bit() is done
> with inline asm.

Nope. Look again.

test_bit() with a constant number is done very much in C, and very much on 
purpose. _Exactly_ to allow the compiler to combine these kinds of things.

> And:
> 
> +		if (!test_bit(WORK_STRUCT_PENDING, &work->management))
> 
> Should possibly be:
> 
> +		if (!work_pending(work))

Yeah, that's a worthy cleanup.

		Linus
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