Re: [PATCH 10/19] workqueue: update cwq alignement and make one moreflag bit available

[Jeff Garzik]

On 10/01/2009 09:05 AM, David Howells wrote:
> Tejun Heo<tj@xxxxxxxxxx>  wrote:
>
> > +enum {
> > +	WORK_STRUCT_PENDING	= 0,	/* work item is pending execution */
> > +
> > +	/*
> > +	 * Reserve 3bits off of cwq pointer.  This is enough and
> > +	 * provides acceptable alignment on both 32 and 64bit
> > +	 * machines.
> > +	 */
> > +	WORK_STRUCT_FLAG_BITS	= 3,
> > +
> > +	WORK_STRUCT_FLAG_MASK	= (1UL<<  WORK_STRUCT_FLAG_BITS) - 1,
> > +	WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
> > +};
>
> There's some great enum abuse going on here:-)

The quoted code is a standard kernel technique for creating typed 
constants that are visible to the C compiler (rather than CPP) and debugger.

It is found in a great many Linux kernel drivers at this point, and is 
definitely not abuse, IMO.

	Jeff


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/