From: Andi Kleen <redacted>
Date: Mon, 19 Mar 2007 11:57:28 +0100

On Monday 19 March 2007 00:46, Jeremy Fitzhardinge wrote:

quoted

Andi Kleen wrote:
For example, say we wanted to put a general call for sti into entry.S,
where its expected it won't touch any registers.  In that case, we'd
have a sequence like:

    push %eax
    push %ecx
    push %edx
    call paravirt_cli
    pop %edx
    pop %ecx
    pop %eax

This cannot right now be expressed as inline assembly in the unwinder at all 
because there is no way to inject the push/pops into the compiler generated
ehframe tables.

[BTW I plan to resubmit the unwinder with some changes]

It's inability to handle sequences like the above sounds to me like
a very good argument to _not_ merge the unwinder back into the tree.

To me, that unwinder is nothing but trouble, it severly limits what
cases you can use special calling conventions via inline asm (and we
have done that on several occaisions) and even ignoring that the
unwinder only works half the time.

Please don't subject us to another couple months of hair-pulling only
to have Linus yank the thing out again, there are certainly more
useful things to spend time on :-)