why it's globle mutex,Can't different MobileAuthenticator instance GetConfirmations in parallel?

Can't different MobileAuthenticator instance GetConfirmations in parallel?
Correct. This has to be a global semaphore.
no, I have tried,getting confirmations can be in parallel,accepting confirmation has to be send one by one
And you're right, nobody said that you can't fetch confirmations in parallel. That semaphore is limiting number of requests over time, not their pure existance. Refer to issue #769 and configuration section on confirmations limiter delay. I checked personally that part during implementation and I also know how it works - if you think I'm wrong then try to fetch confirmations 10 times in a very short time, one after another. You'll get a block after 5 or 7.
ASF is working properly regarding that. There is only small improvement done as part of https://github.com/JustArchi/ArchiSteamFarm/commit/2a5a60e0943be4d9d56adddbd4621d08b88d833f in terms of this.
get it,thanks