Is it possible to apply this patch to my current installation?  We use this
box in production and the reboots that we're experiencing are an
inconvenience.

Is there is a walkthrough on how to apply this patch?  If not, could your
provide the steps necessary to apply successfully?  I would greatly
appreciate it.

Thank you

On Mon, Dec 12, 2011 at 4:00 AM, Dave Chinner [off-list ref] wrote:

On Mon, Dec 12, 2011 at 06:13:11AM +0100, Andi Kleen wrote:

quoted

quoted

It's ~180 bytes, so it's not really that small.

Quite small compared to what real code uses. And also fixed
size.

quoted

quoted

is on the new stack. ISTs are not used for interrupts, only for
some special exceptions.

IST = ???

That's a hardware mechanism on x86-64 to switch stacks
(Interrupt Stack Table or somesuch)

With ISTs it would have been possible to move the the pt_regs too,
but the software mechanism is somewhat simpler.

quoted

at the top of the stack frame? Is the stack unwinder walking back
across the interrupt stack to the previous task stack?

Yes, the unwinder knows about all the extra stacks (interrupt
and exception stacks) and crosses them as needed.

BTW I suppose it wouldn't be all that hard to add more stacks and
switch to them too, similar to what the 32bit do_IRQ does.
Perhaps XFS could just allocate its own stack per thread
(or maybe only if it detects some specific configuration that
is known to need much stack)

That's possible, but rather complex, I think.

quoted

It would need to be per thread if you could sleep inside them.

Yes, we'd need to sleep, do IO, possibly operate within a
transaction context, etc, and a workqueue handles all these cases
without having to do anything special. Splitting the stack at a
logical point is probably better, such as this patch:

http://oss.sgi.com/archives/xfs/2011-07/msg00443.html

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com

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Ryan C. England
Corvid Technologies <http://www.corvidtec.com/>
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