Hello rt I am working on porting a vxworks application from vxworks to linux preempt-rt. this application is hard real time application as it controls a robot. here are the current difficulties i face, and i hope to get this community views: 1. vxworks rt priority range scales up to 255 and not 100 which is not enough. Compiling kernel with RT_MAX_PRIO set to 255 ( 3.0 even without preemprt rt ) and executing cyclictest crashes kernel ( NULL pointer in pick_next_task_rt +0x88 ). So naive approach doesn't work. How do i increase MAX_RT_PRIO to higher value, even in the cost of recompiling an entire system ( all os user space code is recompiled with a sanitized kernel headers ). 2. global critical section vxworks does not have the notion of a virtual address space. so code that is "user space" oriented is executing side by side to an interrupt , this leads to "cli"-like global locks in a vxworks world. so in linux.. one solution is to "iopl(3)" and then "sti/cli" in user space , this is good for UNI processors machines, but assuming preempt-rt will run smp machines it is not good. also, disabling interrupts is considered bad practice in preempt-rt. another solution is to increase the executing thread priority to the highest value possible, i believe it is theoretically correct assuming i have full control over the entire operating system. anyone experienced with sort of problems ? or tried any of the above with success ? 3. vxworks target shell. vxworks provides a shell-like access to its system, and since all tasks share address space it is possible to access all globals in the c code just like in gdb, examine stacks and so on without disturbing the rt task whatsoever. I need this feature in linux per-process. At the moment i did not find anything like vx-target shell in linux. gdb/ptrace is out of the question as they influence the rt task behavior. Currently I think to create a thread that is part of to the process address space. this thread is based on libcli, and it it means should integrate it with pstack code and nm code. so before i start writing piles of code, any other ideas ? thank you raz -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
