How is semop performed?

Question

linux

How is semop performed?
Are the operations performed sequentially, as described in the struct array sembuf?
That is, can it be that only a subset of the semaphores are changed while the process is blocked on the next semaphore in the set?

Answer 1

1. semop() is not POSIX, but System V semaphores, it's rather exotic for Linux than the norm - it's included more for compatibility with programs written for ... Solaris, for example.
2. in detail about all synchronization operations (including semop) you can read:
(you can find and download it, there are a lot of it)
3. Stevens writes:
The entire array of operations passed to the semop function is executed by the kernel as a single operation; atomicity is not guaranteed. The kernel performs all of the specified operations, or none of them.