On Tue, 13 Feb 2007, Ingo Molnar wrote: > I'm pleased to announce the first release of the "Syslet" kernel feature > and kernel subsystem, which provides generic asynchrous system call > support: > [...]
Ok, I had little to time review the code, but it has been a long working day, so bear with me if I missed something. I don't see how sys_async_exec would not block, based on your patches. Let's try to follow: - We enter sys_async_exec - We may fill the pool, but that's nothing interesting ATM. A bunch of threads will be created, and they'll end up sleeping inside the cachemiss_loop - We set the async_ready pointer and we fall inside exec_atom - There we copy the atom (nothing interesting from a scheduling POV) and we fall inside __exec_atom - In __exec_atom we do the actual syscall call. Note that we're still the task/thread that called sys_async_exec - So we enter the syscall, and now we end up in schedule because we're just unlucky - We notice that the async_ready pointer is not NULL, and we call __async_schedule - Finally we're in pick_new_async_thread and we pick one of the ready threads sleeping in cachemiss_loop - We copy the pt_regs to the newly picked-up thread, we set its async head pointer, we set the current task async_ready pointer to NULL, we re-initialize the async_thread structure (the old async_ready), and we put ourselves in the busy_list - Then we roll back to the schedule that started everything, and being still "prev" for the scheduler, we go to sleep So the sys_async_exec task is going to block. Now, am I being really tired, or the cachemiss fast return is simply not there? There's another problem AFAICS: - We woke up one of the cachemiss_loop threads in pick_new_async_thread - The threads wakes up, mark itself as busy, and look at the ->work pointer hoping to find something to work on But we never set that pointer to a userspace atom AFAICS. Me blind? :) - Davide - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
