Re: [PATCH v2 1/3] ARM: catch pending imprecise abort on unmask

[Tony Lindgren <tony@atomide.com>]

* Russell King - ARM Linux <linux@arm.linux.org.uk> [151015 09:11]:
> On Thu, Oct 15, 2015 at 08:39:15AM -0700, Tony Lindgren wrote:
> > * Russell King - ARM Linux <linux@arm.linux.org.uk> [151015 08:37]:
> > > On Thu, Oct 15, 2015 at 12:32:20PM +0200, Lucas Stach wrote:
> > > > Install a non-faulting handler just before unmasking imprecise aborts
> > > > and switch back to the regular one after unmasking is done.
> > > > 
> > > > This catches any pending imprecise abort that the firmware/bootloader
> > > > may have left behind that would normally crash the kernel at that point.
> > > > As there are apparently a lot of bootlaoders out there that do such a
> > > > thing it makes sense to handle it in the common startup code.
> > > > 
> > > > Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> > > 
> > > Much better.  Please feel free to add it to the patch system, thanks.
> > > 
> > > I think, given that the original seems to be breaking platforms, this
> > > patch needs to go into -rc kernels, right?
> > 
> > Hmm do we still see a trace where the issue happened though with this
> > one?
> 
> That's not the intention of this specific patch.
> 
> This is solely to detect the bootloader induced imprecise exception,
> nothing more.  A backtrace for that won't be useful in any shape or
> form - in fact, the backtrace will be well known (it'll be from the
> site where the imprecise exceptions are unmasked.)
> 
> Any imprecise exception which happens after this will be handled in
> the normal way: it'll raise a kernel oops, and that will have all the
> details that a kernel oops normally has.

OK makes sense.

> The difference is, rather than the boot loader provoking the kernel to
> oops at this point, we're able to report the event and continue on.

OK

Tony