(process management) 03. Synchronization mode of process and thread


Synchronization mode of process and thread:

The synchronization methods of processes and threads are basically the same, mainly locks and semaphores

1. Lock

Lock is to use the exclusivity and mutex of resources to ensure the synchronization of processes (threads).

In short, a process (thread) obtains a lock on a resource, which is equivalent to that the process (thread) obtains the right to use the resource and refuses to be occupied by other processes (threads). However, other processes (threads) can get the lock, but they will be blocked. They can’t get the lock of the resource until the lock of the resource is released.

2. Semaphore

Semaphore mechanism is similar to lock mechanism. Semaphores will record the number of resources. Whenever a process (thread) requests a certain number of resources, it will update the number of free resources; Once a process (thread) requests more resources than the number of free resources, it will send a signal of insufficient resources to prompt that the process (thread) cannot obtain enough resources and block until there are enough resources.

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