This appears to be a duplicate of MDEV-21330.

This issue differs from MDEV-21330 in a subtle way: it's asking for InnoDB to print the thread ID of the thread holding the mutex, while MDEV-21330 is asking for InnoDB to print the same thread info in release builds as it currently does in debug builds. Debug builds currently print the following information:

• The thread ID of the thread waiting for the semaphore.
• The type of semaphore. (i.e. mutex or RW-latch)
• The source file and line where the thread is waiting for the lock.
• The source file and line where the semaphore was last reserved.

I agree that the thread ID of the thread holding the mutex should be printed as well. However, we still need the above information to be printed too. The thread ID is not always helpful on its own. The problem is that some threads do not appear in SHOW ENGINE INNODB STATUS, so the thread ID is not always enough to identify the thread. In that case, the information requested by MDEV-21330 (which is currently only available in debug builds) can be used to identify the thread.

My perspective of this is that MDEV-21330 and MDEV-22527 are asking for the same thing: the lock monitor in the error log and SHOW ENGINE INNODB STATUS output should allow you to properly diagnose semaphore waits. Each of the issues is asking for a different piece of that:

1.) MDEV-21330 is basically asking for the output to include what the thread is doing while holding the semaphore. This code is already written, but it is only enabled in debug builds for some reason.
2.) MDEV-22527 is basically asking for the output to include which thread is holding the semaphore. This code may not be written at all yet.

Both pieces of this information appear to be necessary for proper diagnostics, because not all threads appear in the lock monitor in the error log or SHOW ENGINE INNODB STATUS output. For those threads, #2 may not be enough information to diagnose the problem. In that case, you may need #1 to determine if the semaphore is held by some internal InnoDB thread that is mostly hidden from the user.

MDEV-21330 introduced two variables to write on every lock() and this MDEV requests to add another variable thread_id which will become a scalability issue too similar to the case of MDEV-21330

The semaphore wait section was removed in MDEV-21452. We could theoretically implement the requested diagnostics in older major versions than 10.6 only.

Marko, I don't see this removal in the ticket description. Why would we remove important and critical observability from our engine?