The logic to detect if the irq stack was already in use with
raw_spin_trylock() is wrong, because it will generate a "trylock failure
on UP" error message with CONFIG_SMP=n and CONFIG_DEBUG_SPINLOCK=y.

arch_spin_trylock() can't be used either since in the CONFIG_SMP=n case
no atomic protection is given and we are reentrant here. A mutex didn't
worked either and brings more overhead by turning off interrupts.

So, let's use the fastest path for parisc which is the ldcw instruction.

Counting how often the irq stack was used is pretty useless, so just
drop this piece of code.
Signed-off-by: NHelge Deller <deller@gmx.de>

Show number of floating point assistant and unaligned access fixup
handler in /proc/interrupts file.
Signed-off-by: NHelge Deller <deller@gmx.de>

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: NHelge Deller <deller@gmx.de>

Fix up build error on UP and show correctly number of function call
(ipi) irqs.
Signed-off-by: NHelge Deller <deller@gmx.de>

Add framework and initial values for more fine grained statistics in
/proc/interrupts.
Signed-off-by: NHelge Deller <deller@gmx.de>

Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NKyle McMartin <kyle@mcmartin.ca>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!