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47. System V Semaphores > Disadvantages of System V Semaphores

Disadvantages of System V Semaphores

System V semaphores have many of the same disadvantages as message queues (Disadvantages of System V Message Queues), including the following:

  • Semaphores are referred to by identifiers, rather than the file descriptors used by most other UNIX I/O and IPC mechanisms. This makes it difficult to perform operations such as simultaneously waiting both on a semaphore and on input from a file descriptor. (It is possible to resolve this difficulty by creating a child process or thread that operates on the semaphore and writes messages to a pipe monitored, along with other file descriptors, using one of the methods described in Chapter 63.)


  

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