Re: [PATCH] pci_get_device call from interrupt in reboot fixups

From: Andrew Morton
Date: Tue Aug 07 2007 - 03:46:01 EST


On Tue, 7 Aug 2007 00:24:37 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> > Andrew, I really don't want to change the PCI core to handle this, as we
> > finally fixed a lot of issues with drivers trying to walk these lists
> > from interrupt context. So if you want to just hide the warning message
> > as we are shutting down, that's fine with me. Or just don't do the
> > fixups. But grabbing a reference to the pci device is unsafe in my
> > opinion and I do not want to do that.
> >
>
> OK, good decision ;)
>
> One approach would be for some brave soul to pick his way through
> the reboot code and ensure that we are correctly and reliably setting
> system_state to SYSTEM_RESTART, then test that in __might_sleep().
>
> But this does suppress somewhat-useful debugging just because of sysrq-B
> and I really wouldn't want to utilise the horrid system_state any more that
> we are presently doing. I think on balance that it would be better if we
> could do something more targetted, like modify emergency_restart() to test
> in_interrupt() and to then apologetically set some well-named global flag
> which will shut up __might_sleep(). Pretty foul, but I can't think of
> anything better.

ok, this might be better. How about we just stop calling mach_reboot_fixups()
at sysrq-B time?

> > >> handle_sysrq
> > >> machine_emergency_restart
> > >> mach_reboot_fixups
> > >> pci_get_device
> > >> pci_get_subsys
> > >> down_read
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