No, when the process is waiting on read/write to a file, it cannot be interrupted. The signal literally will not reach it until the syscall finishes. This is a

No, when the process is waiting on read/write to a file, it cannot be interrupted. The signal literally will not reach it until the syscall finishes. This is a deficiency of Linux design inherited from Unix and something that is being addressed over time. However it stems from the real requirement that a device can't just have its operation cancelled, once you've asked the HDD to read a sector, it won't respond until it has finished reading. So the process is stuck in the kernel HDD driver which literally cannot be interrupted. When it's a network or other removable storage obviously interrupts should happen at the media level, but the design did not permit it originally. Currently you can kill an fuse process and NFS has bits to allow signals in the middle of a read, but cifs for example doesn't.