Linux FUTEX_WAIT 和 FUTEX_WAIT_PRIVATE 有什么区别？
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What is the difference between FUTEX_WAIT and FUTEX_WAIT_PRIVATE?
提问by Gabriel Southern
I have been tracing a process with strace and have seen entries such as:
我一直在用 strace 跟踪一个进程，并看到了如下条目：
futex(0x7ffff79b3e00, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x7ffff79b3e00, FUTEX_WAIT_PRIVATE, 2, NULL) = 0
However, when I looked at the man page for futexI have only seen entries such as FUTEX_WAITand FUTEX_WAKE. So my question is what does _PRIVATEthat is appended to the end of these names in my strace output mean? For instance is there any difference between something like FUTEX_WAKEthat is documented in the futex man page and FUTEX_WAKE_PRIVATEthat I see in the strace output or can I assume that they are the same when I am trying to understand what is happening with the program I am debugging.
但是，当我查看futex的手册页时，我只看到了诸如FUTEX_WAITand 之类的条目FUTEX_WAKE。所以我的问题是_PRIVATE在我的 strace 输出中附加到这些名称的末尾是什么意思？例如FUTEX_WAKE，futex 手册页中记录的内容与FUTEX_WAKE_PRIVATE我在 strace 输出中看到的内容之间是否有任何区别，或者当我试图了解我正在调试的程序发生的情况时，我是否可以假设它们是相同的。
采纳答案by je4d
This is an optimization done by linux/glibc to make futexes faster when they're not shared between processes. Glibc will use the _PRIVATEversions of each of the futex calls unless the PTHREAD_PROCESS_SHAREDattribute is set on your mutex
这是由 linux/glibc 完成的优化，当 futex 不在进程之间共享时使它们更快。Glibc 将使用_PRIVATE每个 futex 调用的版本，除非PTHREAD_PROCESS_SHARED在您的互斥锁上设置了该属性
It's explained in more detail here: http://lwn.net/Articles/229668/
这里有更详细的解释：http: //lwn.net/Articles/229668/
For the purposes of your debugging, you can just ignore the _PRIVATEsuffixes
出于调试目的，您可以忽略_PRIVATE后缀
