Add support for the flexible mmap memory layout (as described in
http://lwn.net/Articles/91829). This is especially very interesting on
parisc since we currently only support 32bit userspace (even with a
64bit Linux kernel).
Signed-off-by: Helge Deller <deller@gmx.de>
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: Helge 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: Helge Deller <deller@gmx.de>
Default kernel stack size on parisc is 16k. During tests we found that the
kernel stack can easily grow beyond 13k, which leaves 3k left for irq
processing.
This patch adds the possibility to activate an additional stack of 16k per CPU
which is being used during irq processing. This implementation does not yet
uses this irq stack for the irq bh handler.
The assembler code for call_on_stack was heavily cleaned up by John
David Anglin.
CC: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
