Kaz Kylheku 在 2017年2月24日 星期五上午11:20:10 [UTC+8] 的信中寫道：

On 2017-02-24, zhan...@conew.com <zhan...@conew.com> wrote:

在 2012年4月25日星期三 UTC+8下午11:17:09，Noob写道：

^^^^^

Hello everyone,

The (proprietary) OS I've been working with provides two "types"
of semaphores: fifo or prio.

This discussion is useful.

It's also almost five years old and not going on any more.

According to below link, I think it doesn't guarantee any order. https://man7.org/linux/man-pages/man2/futex.2.html

FUTEX_WAKE (since Linux 2.6.0)
This operation wakes at most val of the waiters that are
waiting (e.g., inside FUTEX_WAIT) on the futex word at the
address uaddr. Most commonly, val is specified as either
1 (wake up a single waiter) or INT_MAX (wake up all
waiters). No guarantee is provided about which waiters
are awoken (e.g., a waiter with a higher scheduling
priority is not guaranteed to be awoken in preference to a
waiter with a lower priority).

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