gnu asm help...
Quoted 11 lines · Richard B. Johnson
Quoted 10 lines · Timur Tabi
Oh, I see the problem. You could do something like this:
cli
mov %0, %%eax
inc %%eax
mov %%eax, %0
stiand then return eax, but that won't work on SMP (whereas the "lock inc" does). Doing a global cli might work, though.
Use spinlocks instead of global cli. Global cli can take milliseconds.
Quoted 2 lines
The Intel book(s) state that an interrupt is not acknowledged until so many clocks (don't remember the number) after a stack operation.
Reread it. It says 'after operation with ss' - that is after "mov xxxx,%ss" or "pop %ss", as it is expected that next instruction will be "movl yyyy,%esp".
Before "lss ...." (it is lss in intel mnemonic...) was invented, you could not switch your stack safely without this feature, as NMI could arrive in the middle of your stack switch without blocking all interrupts after "mov xxxx,%ss".
BTW, if you chain "mov %eax,%ss" back to back, they are executed in pairs - irq can arrive after even mov, but cannot after odd (at least on PII and PIII). But it is a bit off topic for L-K (except that we can try other clones, maybe someone got it wrong?)
Best regards,
Petr Vandrovec [email protected]