On Monday, December 6, 2004 8:59 am, Jesse Barnes wrote:
> On Monday, December 6, 2004 4:42 am, Hidetoshi Seto wrote:
> > Jesse Barnes wrote:
> > > On Friday, December 3, 2004 8:31 am, Jesse Barnes wrote:
> > >>This patch adds support for sending a SIGBUS to a userspace application
> > >>using /proc/bus/pci to drive a device if an I/O error occurs.  We're
> > >> using this in house for the X server's BIOS emulator and it seems to
> > >> be working well.
> > >>
> > >>The idea is to track mmaped /proc/bus/pci regions so that the machine
> > >> check handler is able to properly determine which process is
> > >> responsible for any faults that occur (ia64 is interesting in that the
> > >> error may not occur in the process context that actually generated the
> > >> bad reference). If a match is found, a SIGBUS is sent to the process,
> > >> along with the address that caused the fault.  The machine check
> > >> record is then cleared and recovery takes place (the assumption is
> > >> that the signal to userspace is a sufficient record of the error).
> >
> > Cool!
> > BTW I have some short comments.
>
> Does this look a little better?  I've removed the clearing of the error
> records too, in light of Keith's patch to clear them out quickly if they're
> corrected (though I'll need more additions to set the recovered flag
> correctly).
>
> > force_sig_info() takes spinlock in it... I think calling this isn't safe
> > on MCA.
>
> This is the only bit I'm unsure about.  I can't just add a spin_trylock
> version, since the call path for send_sig_info calls the slab allocator,
> which takes other locks.
>
> Assuming that only the CPU that caused the MCA is in the MCA handler (i.e.
> rendezvous doesn't occur), then the only time that one of the spinlocks
> could hang is if the current CPU also owned it, right?  Hmm, maybe the
> ia64_spinlock_contention routine could check for a machine check condition
> and promote the failure to an uncorrectable one in that case?  That's
> pretty ugly though...

Ugg, again I forget to post the patch.  Here it is.

Jesse