Linus Torvalds wrote:
On Tue, 20 Mar 2007, Zachary Amsden wrote:
Actually, I was thinking the irq handlers would just not mess around with
eflags on the stack, just call the chip to ack the interrupt and re-enable
hardware interrupts when they left, since that is free anyway with the iret
Linus Torvalds wrote:
On Tue, 20 Mar 2007, Zachary Amsden wrote:
void local_irq_restore(int enabled)
{
pda.intr_mask = enabled;
/*
* note there is a window here where softirqs are not processed by
* the interrupt handler, but that is not a problem, since it will
* get done
Jeremy Fitzhardinge wrote:
Zachary Amsden wrote:
I think Jeremy's idea was to have interrupt handlers leave interrupts
disabled on exit if pda.intr_mask was set. In which case, they would
bypass all work and we could never get preempted.
Yes, I was worried that if we left th
Matt Mackall wrote:
I don't know that you need an xchg there. If you're still on the same
CPU, it should all be nice and causal even across an interrupt handler.
So it could be:
pda.intr_mask = 0; /* intr_pending can't get set after this */
Why not? Oh, I see. intr_mask is inverted for
Jeremy Fitzhardinge wrote:
Yeah, disable interrupts, and set a flag that the fake "sti" can test, and
just return without doing anything.
(You may or may not also need to do extra work to Ack the hardware
interrupt etc, which may be irq-controller specific. Once the CPU has
accepted the inte
Andi Kleen wrote:
One thing I was pondering was to replace the expensive popfs with
bt $IF,(%rsp)
jnc 1f
sti
1:
But would be mostly a P4 optimization again and I'm not 100% sure it is
worth it.
Worth it on 32-bit. On AMD64, probably not. On Intel 64-bit, maybe,
but less important t
Rusty Russell wrote:
On Mon, 2007-03-19 at 11:38 -0700, Linus Torvalds wrote:
On Mon, 19 Mar 2007, Eric W. Biederman wrote:
True. You can use all of the call clobbered registers.
Quite often, the biggest single win of inlining is not so much the code
size (although if done righ
Jeremy Fitzhardinge 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
