In Linux, while an ISR is being executed for an interrupt line, I understand that Linux will disable the interrupt in all the processors and optionally (with IRQF_DISABLED set), it can also disable all the interrupts in the current processor. So, there is no need for the ISR to be re-entrant.
But, say that I provide the same ISR for requesting more than one interrupt lines. In this case, while the ISR is in execution for an interrupt, isn't there a possibility that another interrupt line may get raised and call the same ISR? For such cases, is it mandatory for the ISR to be re-entrant?