Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

Alan Cox
2007-12-12T16:19:48Z

There is another reason we can't just do a dumb changeover - two actually

#1: Some drivers are using inb_p/outb_p in PCI cases which are going to
cause PCI posting changes. Most are probably just wrong in the first
place but they need hand checking

#2: We've got SMP cases that only 'work' because the odds of splitting
the outb and the following port 0x80 cycle, which locks the bus, are tiny.

That is we've got

CPU1 CPU2
main path irq path
outb
outb

inb 0x80
inb 0x80

races in one or two spots.