cli()/sti() clarification

Thankyou all for explaining the system call internals to me. Feel like an idiot now :)

Marco Colombo: As for what I am trying to achieve, it is simply this. I need to do plot extraction from radar raw returns. The scan time for one revolution is 2.44 secs. I need to extract plots for each pi/2 radians in less than 2.44/4 secs. I have already optimized the extraction algo upto SSE2 in assembly and am running the process as realtime, but it just cant seem to cut it. So now I am going to try and block interrupts while I do the DSP.

Regards,
Irfan Hamid.