uninterruptable parts of code

DocBexter · 09-10-2003, 05:06 PM

ive been playing around with sched_fifo but it doesnt seem to do a good job since small cpu loads just interrupt my critical code...

so im asking if there is a command like "do-not-disturb" so some parts of code get processed without interruption ??

the basic idea is:

do_sth_meaningless();
do_not_disturb();
do_critical_code();
please_disturb();

Proud · 09-10-2003, 05:16 PM

Vague info:
There's the ability to set the nice-ness of an executed process in linux, and also iirc each app gets 10millisecond time slices of uninterrupted execution (dunno about IRQ handling) by default. But I really cant help more

DocBexter · 09-10-2003, 05:45 PM

nice is set to -20
sched_fifo to set_max_prio

but this all doesnt help much ... some soft or hard irq interrupts my code and i can say good bye to my critical code ....

kev82 · 09-10-2003, 07:19 PM

just imagine if there was a userspace 'do-not-disturb' function, i would give it 30s before a script-kiddie came along and did

Code:

int main()
{
    do_not_disturb();
    while(1);
    return 0;
}

so you can see why its a terrible idea. if your doing some low level hardware stuff and really do need a do-not-distrurb then do your stuff in kernel mode. if you could explain why you need it in userspace then perhaps we can help.

DocBexter · 09-11-2003, 04:33 AM

this statement would be ok if we were talking about java or script languages but c needs to be powerful - i mean this is not a place like a white box where we put kiddies in so they can jump against the walls ....

but since i didnt find anything that helps ill be really goin to kernel space and use the lock hammer "cli sti"

kev82 · 09-11-2003, 05:56 AM

Quote:

this statement would be ok if we were talking about java or script languages but c needs to be powerful - i mean this is not a place like a white box where we put kiddies in so they can jump against the walls ....

its got nothing to do with C, its to do with the kernel. unix kernels(and NT kernels and probably win95+) dont provide a userspace function with the ability to halt the system, nor do they let you do direct hardware io, it would be absurd to do so.

Quote:

but since i didnt find anything that helps ill be really goin to kernel space and use the lock hammer "cli sti"

im not a kernel programming expert but i wouldnt use the machine instructions directly, i would find their wrappers because the 2.5/2.6 series kernel allow user mode to preempt kernel mode, which would be very bad if you had cli'ed and then it jumped into user mode.

if your not writing a hardware driver, then i cant see any valid reason why you need to not be disturbed by the system, maybe your thinking about your problem the wrong way, as i say if you explain what your trying to do then maybe we can help.