Question

Find correct statements:

1. The read system call to fetch data from a file always blocks the invoking process.
2.  During filesystem operations, if the file system implementation ensures that changes to data blocks of a file are flushed to disk before changes to metadata blocks (like inodes and bitmaps), then the file system will never be in an inconsistent state after a crash, and a file system checker need not be run to detect and fix any inconsistencies.

3. Interrupt-based device drivers give superior performance to polling-based drivers because they eliminate the time spent by the CPU in copying data to and from the device hardware.

4. Consider a process in kernel mode that acquires a spinlock. For correct operation, it must disable  interrupts on its CPU core for the duration that the spinlock is held, in both single core and multi core systems.

Comments

1. When the system call occurs we need to switch to kernel mode, so the invoking process would be blocked if it was a blocking system call not always. This should be false.

3. Interrupt based gives superior performance than polling based because in polling the cpu is constantly checking the status register for interrupts, so polling is less efficient as the hardware devices are slow.
So, the statement is true but the reason i think is not correct.

4. If spin-lock is in a single processor then we have to disable the CPU interrupt, if we not then there may be deadlock, if the interrupting process tries to access the variable that has been locked, but in multi-processor if we just disable the interrupts for the local core it should be enough.

I didn't get what would happen for statement $2$ , Sir, please check my reasoning and provide answer for the same.