Re: can somebody explain barrier() macro ?

Erik Mouw (J.A.K.Mouw@ITS.TUDelft.NL)
Tue, 20 Feb 2001 21:04:37 +0100


On Tue, Feb 20, 2001 at 12:50:54PM -0700, hiren_mehta@agilent.com wrote:
> barrier() is defined in kernel.h as follows :
>
> #define barrier() __asm__ __volatile__("": : :"memory")
>
> what does this mean ? is this like "nop" ?

It's a write barrier. It prevents the compiler from optimising writes
to memory: all outstanding writes should be done before the program
flow crosses the barrier().

Erik

-- 
J.A.K. (Erik) Mouw, Information and Communication Theory Group, Department
of Electrical Engineering, Faculty of Information Technology and Systems,
Delft University of Technology, PO BOX 5031,  2600 GA Delft, The Netherlands
Phone: +31-15-2783635  Fax: +31-15-2781843  Email: J.A.K.Mouw@its.tudelft.nl
WWW: http://www-ict.its.tudelft.nl/~erik/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/