parisc: implement irq stacks - part 2 (v2)

This patch fixes few build issues which were introduced with the last
irq stack patch, e.g. the combination of stack overflow check and irq
stack.

Furthermore we now do proper locking and change the irq bh handler
to use the irq stack as well.

In /proc/interrupts one now can monitor how huge the irq stack has grown
and how often it was preferred over the kernel stack.

IRQ stacks are now enabled by default just to make sure that we not
overflow the kernel stack by accident.

Signed-off-by: Helge Deller <deller@gmx.de>
parisc: fix SMP races when updating PTE and TLB entries in entry.S

Currently, race conditions exist in the handling of TLB interruptions in
entry.S.  In particular, dirty bit updates can be lost if an accessed
interruption occurs just after the dirty bit interruption on a different
cpu.  Lost dirty bit updates result in user pages not being flushed and
general system instability.  This change adds lock and unlock macros to
synchronize all PTE and TLB updates done in entry.S.  As a result,
userspace stability is significantly improved.

Signed-off-by: John David Anglin  <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
parisc: make default cross compiler search more robust (v3)

People/distros vary how they prefix the toolchain name for 64bit builds.
Rather than enforce one convention over another, add a for loop which
does a search for all the general prefixes.

For 64bit builds, we now search for (in order):
	hppa64-unknown-linux-gnu
	hppa64-linux-gnu
	hppa64-linux

For 32bit builds, we look for:
	hppa-unknown-linux-gnu
	hppa-linux-gnu
	hppa-linux
	hppa2.0-unknown-linux-gnu
	hppa2.0-linux-gnu
	hppa2.0-linux
	hppa1.1-unknown-linux-gnu
	hppa1.1-linux-gnu
	hppa1.1-linux

This patch was initiated by Mike Frysinger, with feedback from Jeroen
Roovers, John David Anglin and Helge Deller.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Jeroen Roovers <jer@gentoo.org>
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Merge branch 'parisc-for-3.10' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux

Pull parisc update from Helge Deller:
 "The second round of parisc updates for 3.10 includes build fixes and
  enhancements to utilize irq stacks, fixes SMP races when updating PTE
  and TLB entries by proper locking and makes the search for the correct
  cross compiler more robust on Debian and Gentoo."

* 'parisc-for-3.10' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: make default cross compiler search more robust (v3)
  parisc: fix SMP races when updating PTE and TLB entries in entry.S
  parisc: implement irq stacks - part 2 (v2)