interrupt service routine in qnx? - c

Question

Scenario : Client is sending a data and the server is receving the data from client via ethernet layer (udp). When the server receives a data from the client on the ip layer (kernel). It interrupts the kernel and kernel as to execute the data by the client, so I want to create a interrupt service function to catch the interrupt from the network service card.
I am using Interruptattach api to handle the interrupt from the network interface card and sigevent structure to call the specific function.
http://www.qnx.com/developers/docs/6.3.0SP3/neutrino/lib_ref/i/interruptattach.html#HandlerFunction
is it the right way to handle interrupts in qnx ??
volatile int id1, id2, id3;
const struct sigevent *handler1(void *area, int id1)
{
volatile double KernelStartExecutionTime;
KernelStartExecutionTime = GetTimeStamp(); // calculating the time when the kernel starts executing
TASK1(Task2ms_Raster);
return (NULL);
}
const struct sigevent *handler2(void *area, int id2)
{
volatile double KernelStartExecutionTime;
KernelStartExecutionTime = GetTimeStamp(); // calculating the time when the kernel starts executing
TASK2(Task10ms_Raster);
return (NULL);
}
const struct sigevent *handler3(void *area, int id3)
{
volatile double KernelStartExecutionTime;
KernelStartExecutionTime = GetTimeStamp(); // calculating the time when the kernel starts executing
TASK3(Task100ms_Raster);
return (NULL);
}
/*kernel calls attach the interrupt function handler to the hardware interrupt specified by intr(i.e irq) */
// InterruptAttach() : Attach an interrupt handler to an interrupt source
// interrupt source is handler1 for this example
void ISR(void)
{
volatile int irq = 0; //0 : A clock that runs at the resolution set by ClockPeriod()
ThreadCtl (_NTO_TCTL_IO, NULL);
id1 = InterruptAttach(irq, &handler1, NULL, 0, 0);
id2 = InterruptAttach(irq, &handler2, NULL, 0, 0);
id3 = InterruptAttach(irq, &handler3, NULL, 0, 0);
}
int main(int argc, char *argv[])
{
Xcp_Initialize();
CreateSocket();
ISR(); //function call for ISR
return 0;
}
another question : if I want to call another function in the sigevent structure then should I use another ISR for that (i.e. how to handle multiple function from the interrupt)?
I modified my code as above. Will it be efficient if I do like above. One ISR function with InterruptAttach API for three different handler.

Answer 1

This is a bad approach: Interrupt (IRQ) handlers are not interruptable. That means: 1. your computer will lock up when you do a lot of work in them and 2. you can't call every method.
The correct approach is to receive the IRQ, call a handler. The handler should create a memory structure, fill it with the details what needs to be done and adds this "task data" to a queue. A background thread can then wait for elements in the queue and do the work.
That way, IRQ handlers will be small and fast. Your background thread can be as complex as you like. if the thread has a bug, the worst that can happen is that it breaks (make the IRQ handler throw away events when the queue is full).
Note that the queue must be implemented in such a way that adding elements to it never blocks. Check the documentation, there should already be something that allows several threads to exchange data; the same can be used for IRQ handlers.