Hi, Jan,
now, the rtdev of eth1394 can be seen thru "rtifconfig" and an ip address
can be given to it. But when I run "rtroute solicit" to add the local ip to
the route table, it crashes and prints a message: "Default Trap Handler:
Vector 14: Suspend RT task c804f7a0". The RT task here is born durng insmod
the rtnet module. But it is not the RT task of stack manager. If I only load
rtnet module, from /proc/rtai/scheduler, I will see two RT tasks: the RT
task of stack manager which has priority 1 and the unknown RT task which has
priority 1073741823. Do you have any idea where the unknown RT task comes
from? Is it the low priority task for Linux?
Then it is the rtnet_rtpc wrapping task used when some linux process
(like "rtroute solicit") issues a request which requires real-time
context (in this case for sending the ARP request packet). This means
that your transmission path crashes. Add some rtos_prints to see how far you get.
Btw, since the rtos_tasklet_scheduler is also a RT task and it has a higher
priority than stack manager, I give the rtos_tasklet_scheduler priority 1
and lower the stack manager to priority 2. Then I am still confused by the
semaphore problem: when the rtos_tasklet_scheduler signals the semaphore,
will it be preempted by stack manager?
No, in this case the RTAI scheduler detects that the calling task has a higher prio than the woken up task - and the wakeup call returns to your tasklet scheduler.
And, since the interrupt handler is preemptable by the RT task, which means
when the RT task is running, the interrupt handler hasnt _return_ yet, then
will it make no difference if I directly run the stack manager task in the
interrupt handler?
Actually, the interrupt handler stops at the point the woken up task takes over. That task will NOT run in IRQ context! This means that IRQ are disabled until the task is woken up, but will be enabled again during the task runs. No need to worry.
Jan
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