Re: [Linux-ia64] [patch] 2.4.20-ia64-021210 new spinlock code

David Mosberger
2003-03-27T23:32:52Z

>>>>> On Fri, 28 Mar 2003 10:15:02 +1100, Keith Owens <kaos@sgi.com> said:

Keith> The code does not rely on any implementation specific
Keith> behaviour. Stating that ar.pfs is zero is well defined, it
Keith> means that the caller (rp in r28) of this code has no frame.

No, an unwinder might check whether a stacked register is out of the
current frame and complain if so. Ergo, it's implementation-dependent
behavior.

>> Can you start this discussion?

Keith> I can start it, but it will take months to get agreement on
Keith> the change to the unwind spec, followed by more time for the
Keith> ia64 assemblers to be upgraded to handle the new unwind
Keith> descriptor and more time for users to upgrade to the new
Keith> binutils before the kernel can use any new construct. I want
Keith> to get debugging working for hung ia64 spinlocks this month,
Keith> not in a year's time.

We don't have to wait until all the details are settled. What's
important is that there is a general agreement that the code in
question needs to be accommodated.

Keith> David, you added the NEW_LOCK code even though it never
Keith> worked and could never work. But when I supply code that
Keith> works, is faster, allows for better debugging and performance
Keith> monitoring you quibble about one construct to get the unwind
Keith> data right. I do not understand your priorities here.

Want to guess why the NEW_LOCK code was never enabled? If you want to
add the code with an #if 0, that's fine with me.

--david