Interruptlock/Unlock and the spinlock mystery ;-)

QNX DEVELOPERS General Programming
1

I’ve found a lot of threads discussing this topic, but no answer for my question.

I must switch from InterruptEnable/Disable to Interruptlock/Unlock. Because we use a SMP-Sytem and serveral Ressource-Manager have access via InterruptServiceRoutine to one critical section.
Therefore I need a spinlock-variable.

Do I have to declare a spinlock-variable in a shared memory, so that all processes(RM) uses the same spinlock for the same critical section?

Or can I easily use global variables and every process(RM) uses its own spinlock-variable?

  1. Is it right, that interruptlock() locks all interrupts on one CPU (similar to interruptdisable) and only interrupts from other CPUs can still be enabled and must therefore synchronized by a spinlock-variable?
2

  1. Yes if you want to lock various processes which access the same shared memory

  2. I do not understand the question.

Have you considered using mutex?

3

to 1) o.k. this means I have to create a spinlock in a shared memory, which can be used by all processes

to 2) In former times InterruptDisble disabled the complete interrupt register of the CPU.
Now I have to use interruptlock(spin).
And I dont know how this function works.
Does this function also disable the register for one Core and additional locks the spin or does this function only locks the spin?

4

to 1) I called qnx-support:
→ It’s not recommended to put a spin-variable in the shared memory.
In general, a spinlock should be related to data in a critical section and this data should be related to one process. Therefore a process-wide spinlock shouldn’t be necessary.

to 2) Yes, its correct interruptlock() works in 2 steps.
a) disable interrupt register of one core
b) locks spin