multithreading - What is a semaphore? - Stack Overflow
2008年8月29日 · A semaphore has two parts : a counter, and a list of tasks waiting to access a particular resource. A semaphore performs two operations : wait (P) [this is like acquiring a lock], and release (V)[ similar to releasing a lock] - these are the only two operations that one can perform on a semaphore.
Semaphore implemented with signals not working - Stack Overflow
2024年4月23日 · There is no use for multiple signals being pending at the same time because only one thread can acquire the semaphore, and it will signal when it releases it. The use of sigsuspend() avoids issues with signals being received at an inopportune time, such as between testing the semaphore value and starting to wait.
process - Semaphore wait() and signal() - Stack Overflow
2012年11月23日 · When a task attempts to acquire a semaphore that is unavailable, the semaphore places the task onto a wait queue and puts the task to sleep.The processor is then free to execute other code.When the semaphore becomes available, one of the tasks on the wait queue is awakened so that it can then acquire the semaphore.
Synchronizing processes with semaphores and signals in C
2015年6月13日 · I just tried to compile it on ubuntu linux 14.04 with gcc, The result of the compile is 10 warnings, some of which are very critical, such as when #include'ing ipc.h, must #define _SVID_SOURCE or #define _XOPEN_SOURCE. and passing a size_t (a long int) where a int should be used and incorrect types for semaphore creation (sem_t), returned value from fork() …
about synchronization with using multiple semaphores
2012年10月29日 · A semaphore, if used, just signals the state of the buffer to the consumer and has no connection to the sizes of the packets; it certainly doesn't get incremented by the size of the packet! You would be better advised to use pthread …
C: Signal handling and semaphores - Stack Overflow
2016年1月21日 · server is the server semaphore name, client is the client semaphore name (which doesn't really matter in this case). running (which is actually global) is the variable I use in my signal handler:
java - How to use Semaphores for Signaling? - Stack Overflow
2014年4月24日 · @gstackoverflow, I followed the link, and the information on that page is just wrong. In the last example, where he shows how to use a semaphore as a mutex, he calls semaphore.take() before entering the critical section and semaphore.release() upon leaving it. But the behavior of take() and release() are exactly the opposite of what they should be.
c - Synchronising processes with semaphores - Stack Overflow
2017年4月7日 · Anyway, assuming your get_semaphore() function does the right thing to share the semaphore, there is still a problem because there is no guarantee that, when one process signals the semaphore, the other one will start soon enough for it to grab it again before the first process loops round and grabs it itself.
c - Using Binary Semaphore and Mutex Together - Stack Overflow
2021年5月26日 · In general, I think your design could work. The semaphores are signals for the two tasks to do work. And the mutex protects the shared I2C resource. However, sharing a resource with a mutex can lead to complications. First, your operations tasks are not responsive to new semaphore signals/events while they are waiting for the I2C resource mutex.
In what situation do you use a semaphore over a mutex in C++?
The feature of the semaphore is then that a different thread can "fill" the semaphore back to "full" state. Therefore, mutexes are usually used for the concurrency protection of resources (ie: MUTual EXlusion) while semaphores are used for signaling between threads (like semaphore flags signaling between ships).