digitalmars.D.learn - functions that do not sleep and recovery points
- "akaz" <akaz utopia.com> Jul 21 2012
Hi, In Linux kernel programming, there are some parts that are not allowed to sleep (to be rescheduled). For example: interrupt handlers, softirqs and tasklets. Using functions that can sleep (for example: malloc, semaphores, regular mutexes - unlike spin_locks, etc.) is forbidden inside the above code entities. Currently, this is the responsibility of the programmer. I think that the compiler itself (the gcc) cannot enforce this as it cannot know for sure if a function may block (sleep) or no. But, the question is: - is there any mechanism in D (maybe pure? trusted? notsleeping? or something similar) that could guarantee that a function cannot block? (and enforce that all the function called from inside that function are not-blocking too). More generally, to make such a property transitive and to enforce that? A bit off-topic, there is another question, this time concerning real-time programming: there are two basic strategies for error recovery: forward-recovery (that means, raising an exception and saving what can still be saved) and backward-recovery (that means, going back in time/code to a recovery point and trying to do the job again, maybe using an alternative algorithm). The forward-recovery is classic in C++ and D. The backward-recovery seems to not be so easy: exceptions can be used to detect such an error, but the language itself does not provides a way for establishing a recovery point (I think it might be seen as a program snapshot) to go back to it and then start again (while setting a flag to let "the future" know that an error occurred). Imagine: trying to compute using one fast algorithm but that diverge easily -> failure. Then, roll back and try an alternative algorithm, that is more intensive but convergence is guaranteed etc. You have to know where to roll back. A simple goto will do it? Then, the second question is: - is there any mechanism in D to provide recovery points? Thank you.
Jul 21 2012