Synchronization [was Re: The Magic Show: kernel_map() disappearing]

[Benjamin Herrenschmidt]

On Thu, Jan 14, 1999, Jesper Skov <jskov at cygnus.co.uk> wrote:

>We would want to use eieio for drivers and such accessing their
>controller in a strict serialized manner. We would want to use sync
>for SMP related stuff since it ensures, well, synchronization between
>multiple CPUs wrt memory access.

And I'll add the usual warning: If the device is a PCI device and you
need to make sure that the write actually reached the device (for example
making sure the interrupt enable bits are set before re-enabling the
interrupts on the CPU), you should add a read from the same device (from
the same bus should be enough) to make sure tall the bridges in the path
to the device completed their write.
Remember that a write to PCI is usually a "posted write" and so is
asynchronous, regardless of eieio or sync's done on the CPU.

-- 
           E-Mail: <mailto:bh40 at calva.net>
BenH.      Web   : <http://calvaweb.calvacom.fr/bh40/>





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