Are threads which are executing blocking system calls awoken by interrupts?

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http://unix.stackexchange.com – I've been reading a bit about threads and interrupts. And there is a sections which says that parallel programing using threads is simpler because we don't have to worry about interrupts. However, what is the mechanism in which signals the release of the blocking system call if not an interrupt? Example I read i file in my thread which use a blocking system call to read the file from the disk. During that time, other threads are running. At some point the file is ready to be read from the hard disk. Does it notify the processor of this via a hardware interrupt, so that it can do a conte (HowTos)