Hello, I am reading Robert Love's book on kernel development, and it states that interrupt handlers (that execute on interrupt context) cannot call functions that sleep, because then the ISR's execution thread would be halted and never again rescheduled. Ok, makes sense. However, I couldn't help noticing that, in page 75 of Robert's book, it is stated that, when called upon from ret_from_intr() (arch/i386/kernel/entry.S), schedule() actually RETURNS, and then ret_from_intr() can resume executing. How can schedule() return if it immediately transfers the CPU control to another process? Can it happen when the interrupted process is rescheduled (since it shares its stack with the ISR)? If that is indeed the case, then I failed to see why one must not call sleeping functions from ISRs, since they would resume executing just fine next time the interrupted process was scheduled for execution... I'd apprecciate any feedback on this. Thanks a lot, -- Martim -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
