Merge #16984: util: Make thread names shorter

386ae0f util: Make thread names shorter (Hennadii Stepanov)

Pull request description:

  Thread names at the process level are limited by 15 characters:
  https://github.com/bitcoin/bitcoin/blob/6b2210f1016c9ed96ce470e588e4cb12fa36a900/src/util/threadnames.cpp#L28-L29

  This commit ensures that name `b-httpworker.42` will not be truncated.

  On master (6b2210f):
  ```bash
  hebasto@redcat:~$ ps -T -p $(cat /home/hebasto/.bitcoin/testnet3/bitcoind.pid)
    PID  SPID TTY          TIME CMD
  32647 32647 pts/6    00:00:00 bitcoin-main
  32647 32648 pts/6    00:00:00 QXcbEventReader
  32647 32649 pts/6    00:00:00 bitcoin:disk$0
  32647 32650 pts/6    00:00:00 QDBusConnection
  32647 32651 pts/6    00:00:00 gmain
  32647 32652 pts/6    00:00:00 gdbus
  32647 32653 pts/6    00:00:07 bitcoin-qt-init
  32647 32656 pts/6    00:00:00 bitcoin-scriptc
  32647 32657 pts/6    00:00:00 bitcoin-scriptc
  32647 32658 pts/6    00:00:00 bitcoin-scriptc
  32647 32659 pts/6    00:00:00 bitcoin-schedul
  32647 32660 pts/6    00:00:00 bitcoin-http
  32647 32661 pts/6    00:00:00 bitcoin-httpwor
  32647 32662 pts/6    00:00:00 bitcoin-httpwor
  32647 32663 pts/6    00:00:00 bitcoin-httpwor
  32647 32664 pts/6    00:00:00 bitcoin-httpwor
  32647 32665 pts/6    00:00:00 bitcoin-qt-init
  32647 32668 pts/6    00:00:00 bitcoin-torcont
  32647 32669 pts/6    00:00:00 bitcoin-upnp
  32647 32670 pts/6    00:00:00 bitcoin-net
  32647 32671 pts/6    00:00:00 bitcoin-dnsseed
  32647 32672 pts/6    00:00:00 bitcoin-addcon
  32647 32673 pts/6    00:00:00 bitcoin-opencon
  32647 32674 pts/6    00:00:00 bitcoin-msghand
  32647 32675 pts/6    00:00:00 QThread
  32647 32676 pts/6    00:00:00 QThread
  ```

  With this PR:
  ```bash
  hebasto@redcat:~$ ps -T -p $(cat /home/hebasto/.bitcoin/testnet3/bitcoind.pid)
    PID  SPID TTY          TIME CMD
  25664 25664 pts/0    00:00:00 b-main
  25664 25665 pts/0    00:00:00 QXcbEventReader
  25664 25666 pts/0    00:00:00 bitcoin:disk$0
  25664 25667 pts/0    00:00:00 QDBusConnection
  25664 25668 pts/0    00:00:00 gmain
  25664 25669 pts/0    00:00:00 gdbus
  25664 25670 pts/0    00:00:07 b-qt-init
  25664 25671 pts/0    00:00:00 b-scriptch.0
  25664 25672 pts/0    00:00:00 b-scriptch.1
  25664 25673 pts/0    00:00:00 b-scriptch.2
  25664 25674 pts/0    00:00:00 b-scheduler
  25664 25675 pts/0    00:00:00 b-http
  25664 25676 pts/0    00:00:00 b-httpworker.0
  25664 25677 pts/0    00:00:00 b-httpworker.1
  25664 25678 pts/0    00:00:00 b-httpworker.2
  25664 25679 pts/0    00:00:00 b-httpworker.3
  25664 25680 pts/0    00:00:00 b-qt-init
  25664 25682 pts/0    00:00:00 b-torcontrol
  25664 25683 pts/0    00:00:00 b-upnp
  25664 25684 pts/0    00:00:00 b-net
  25664 25685 pts/0    00:00:00 b-dnsseed
  25664 25686 pts/0    00:00:00 b-addcon
  25664 25687 pts/0    00:00:00 b-opencon
  25664 25688 pts/0    00:00:01 b-msghand
  25664 25689 pts/0    00:00:00 QThread
  25664 25690 pts/0    00:00:00 QThread
  ```

ACKs for top commit:
  MarcoFalke:
    ACK 386ae0f (skimmed the diff on GitHub)
  practicalswift:
    ACK 386ae0f -- diff looks correct
  fanquake:
    ACK 386ae0f - quickly tested on a Debian system.

Tree-SHA512: 8f7f553213a5856943ddba50611814b771e7dc474101a3e1f98259091684c8d0358c541d32011bfe1da7f430225f01a2d6b514a3b7c5aaf671b2ca8fcf155c4a

Author: fanquake

src/util/threadnames.cpp

@@ -57,6 +57,6 @@ static void SetInternalName(std::string name) { }
 
 void util::ThreadRename(std::string&& name)
 {
-    SetThreadName(("bitcoin-" + name).c_str());
+    SetThreadName(("b-" + name).c_str());
     SetInternalName(std::move(name));
 }