Messages in this thread | | | Subject | Re: [PATCH -mm 2/6] cpu_relax(): ide_wait_stat() | From | Alan Cox <> | Date | Wed, 21 Jun 2006 23:19:41 +0100 |
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Ar Mer, 2006-06-21 am 22:59 +0200, ysgrifennodd Andreas Mohr: > Add cpu_relax() to drivers/ide/ide-iops.c/ide_wait_stat().
You don't need cpu_relax() when the loop contains a reference to external memory busses. The CPU will stall on the inb() anyway, and when this occurs processors with multiple-threads will do the right thing implicitly. If you could look at the instruction stream it would look something like
dec count jump out if zero inb read request to the bus [stall] then to the PCI bridge [stall] then eventually to the device [Huge mindbogglingly relativley long period of time stalled] answer finally arrives back over the PCI bus compare ...
Same comment for floppy. Rest look ok
Perhaps this needs documenting however.
Alan
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