linux - 信号量服务员命令

Question

我们想在 Linux 中使用信号量(以及 pthreads)。

我们首先需要知道信号量上的服务员是否正在以 FIFO 方式等待它。这意味着，最后一个等待信号量的人将最后得到它。

谢谢。

Answer 1

来自 http://pubs.opengroup.org/onlinepubs/009696799/functions/sem_post.html 的手册页它不是 FIFO 等待队列:

[PS] [Option Start] If the Process Scheduling option is supported, the thread to be unblocked shall be chosen in a manner appropriate to the scheduling policies and parameters in effect for the blocked threads. In the case of the schedulers SCHED_FIFO and SCHED_RR, the highest priority waiting thread shall be unblocked, and if there is more than one highest priority thread blocked waiting for the semaphore, then the highest priority thread that has been waiting the longest shall be unblocked. If the Process Scheduling option is not defined, the choice of a thread to unblock is unspecified. [Option End]

[SS] [Option Start] If the Process Sporadic Server option is supported, and the scheduling policy is SCHED_SPORADIC, the semantics are as per SCHED_FIFO above. [Option End]