What should be avoided in an interrupt service routine?
Here are some general rules of thumb for operations to avoid:
- Don’t declare any non-static variables inside the handler.
- Avoid blocking function calls.
- Avoid non-reentrant function calls.
- Avoid any processing that takes non-trivial time.
- Avoid operations with locks as you can deadlock your program in an ISR.
Can we use spinlock in ISR?
The answer is yes and no. you can use the up and unlock, but you can’t use down and lock, as these are blocking calls which put the process to sleep and we are not supposed to sleep in interrupt handlers.
What precautions should be taken while writing an interrupt handler?
These precautions typically take the form of special entry and exit code sequences. Save registers and other state information that interrupt-processing might modify to preserve the execution of the code. Prepare the CPU environment before executing the main body of the interrupt handler.
Should we implement mutexes in interrupt handlers?
Mutexes are a perfectly reasonable synchronization primitive to use in interrupts. Of course, you do need to ensure that a thread that holds the mutex can’t be interrupted and run a handler that tries to acquire that same mutex! But writing interrupt handlers isn’t for newbies anyway.
Does spin lock disable interrupts?
There are variants of the spinlock functions that will disable interrupts for you (we’ll see them in the next section). However, a complete discussion of interrupts must wait until Chapter 10. The last important rule for spinlock usage is that spinlocks must always be held for the minimum time possible.
Can you use mutex Semaphore inside an ISR?
With that being the case, it becomes clear that since an ISR cannot acquire a mutex (or any semaphore for that matter – it’s a blocking operation), then it follows that it can’t give the mutex. It is quite possible for an ISR to do give a Binary or Counting semaphore to signal a task that something happens.
How do you execute an interrupt?
Steps to Execute an Interrupt The microcontroller gets the address of the ISR from the interrupt vector table and jumps to it. It starts to execute the interrupt service subroutine, which is RETI (return from interrupt).
Why mutex Cannot be used in ISR?
Vxworks states that mutual exculsion semaphores : Cannot be given inside ISR, while the condition is vaild for binary and counting semaphore.
Can semaphores be used for interrupt context in Linux kernel?
In Linux 2.6. 33, kernel semaphores have been partially replaced by a new “mutex” type, that tries to lock by spinlock methods, but sleeps while spinning, and allows sleeping while held. It may not be used in interrupt handlers (whereas kernel semaphores can do “up” in an interrupt handler).