I am using RTX 4.70 for a project on Cortex M-3. I have added some osXXX calls to the core RTX api.
I am finding that if I have 2 threads (in addition to main plus any timer thread or idle thread) and one is blocked on say an osDelay(), the other thread bombs when it enters kernel mode via a svc trap. I am seeing some form of stack smashing. If I increase OS_TSKCNT from 3 to 4, the problem goes away, but I fear I am postponing a later stack corruption, and that the extra TSK_CNT memory block is buying me some time.
Looking through the RTX4 sources, I am not quite sure whether each thread gets both its own thread mode stack, i.e. tracking PSP, AND its own handler mode stack, tracking MSP, or if there is a single kernel stack and ALL threads 'share it'. Surely for each thread to enter handler mode and exit from it, a dedicated handler mode stack space is needed.
I cannot quite fathom from RTX_Conf_CM.c which #define, if any, is supposed to let me 'increase my handler mode stack space'.
ANY help appreciated. I am using GCC toolchain on Linux, so I don't have an RTX-aware debugger alas. i think at this point that would be very useful.
Stu
Yes, I can see now that OS_TSKCNT should include main.
As with so many scenarios of this type of debugging, I was on the wrong path for quite a while. I wasn't stack smashing at all, but now I am more aware of stack requirements, so this has been a good exercise.
For anyone interested in a 'don't do it like this':
1 An ISR calls os_signalSet( T, S); on a thread T but that thread had already exited (called osThreadExit())
2 ISR sets PendSV and exits
3 PendSV tries to decide who to run and sees a corruption in the RTX data structs, since the os_signalSet did some nasty updates (I haven't quite worked out what)
4 PendSV encounters a Hard Fault.
Curiously, and again I am not fully aware of why, if I bumped OS_TSKCNT to one more that the thread count I actually needed, I would 'get away with' the error condition, but of course not sure for how long.
The problem was in my application code, as is usual ;)