> ok. Is it more of a "gets flushed due to timing out", or a
> specified-for-sure POST flushing property of all out 0x80 cycles going
> to the PCI bridge? I thought PCI posting policy is up to the CPU, it can
> delay PCI space writes arbitrarily (within reasonable timeouts) as long
> as no read is done from the _same_ IO space address. Note that the port
> 0x80 cycle is neither a read, nor for the same address.
Its what appears to happen reliably on real computers.
> i'm wondering, how safe would it be to just dumbly replace outb_p()
> with:
>
> out(port);
> in(port);
Catastrophic I imagine. If the delay is for timing access then you've just
broken the timing, if the port has side effects you've just broken the
driver.
> in these drivers. Side-effects of inb() would not be unheard of for the
> ancient IO ports, but for even relatively old SCSI hardware, would that
> really be a problem?
The specific drivers need reviewing. There are very few uses in PCI space
so it's a minor job.
> ah, i understand. So i guess a stupid udelay_serialized() which takes a
> global spinlock would solve these sort of races? But i guess making them
> more likely to trigger would lead to a better kernel in the end ...
Better to just fix the drivers. I don't think that will take too many
days after everyone is back working.
> doing it - but we'll do the plunge in v2.6.25 and make io_delay=udelay
> the default, hm? Thomas has a real 386DX system, if that doesnt break
For processors with TSC I think we should aim for 2.6.25 to do this and
to have the major other _p fixups done. I pity whoever does stuff like
the scc drivers but most of the rest isn't too bad.
Alan
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