D.4. Comentarios sobre subprocesos RTS

MySQL 5.0

D.4. Comentarios sobre subprocesos RTS

I have tried to use the RTS thread packages with MySQL but stumbled on the following problems:

They use old versions of many POSIX calls and it is very tedious to make wrappers for all functions. I am inclined to think that it would be easier to change the thread libraries to the newest POSIX specification.

Some wrappers are currently written. See for more info.

At least the following should be changed:

should use one argument. should take two arguments. A lot of functions (at least , ) should return the error code on error. Now they return -1 and set .

Another problem is that user-level threads use the signal and this aborts a lot of functions (, , ...). MySQL should do a retry on interrupt on all of these but it is not that easy to verify it.

The biggest unsolved problem is the following:

To get thread-level alarms I changed to wait between alarms with , but this aborts with error . I tried to debug the thread library as to why this happens, but couldn't find any easy solution.

If someone wants to try MySQL with RTS threads I suggest the following:

  • Change functions MySQL uses from the thread library to POSIX. This shouldn't take that long.

  • Compile all libraries with the .

  • Compile .

  • If there are some small differences in the implementation, they may be fixed by changing and .

  • Run . If it runs without any “warning,” “error,” or aborted messages, you are on the right track. Here is a successful run on Solaris:

    Main thread: 1
    Thread 0 (5) started
    Thread: 5  Waiting
    process_alarm
    Thread 1 (6) started
    Thread: 6  Waiting
    process_alarm
    process_alarm
    thread_alarm
    Thread: 6  Slept for 1 (1) sec
    Thread: 6  Waiting
    process_alarm
    process_alarm
    thread_alarm
    Thread: 6  Slept for 2 (2) sec
    Thread: 6  Simulation of no alarm needed
    Thread: 6  Slept for 0 (3) sec
    Thread: 6  Waiting
    process_alarm
    process_alarm
    thread_alarm
    Thread: 6  Slept for 4 (4) sec
    Thread: 6  Waiting
    process_alarm
    thread_alarm
    Thread: 5  Slept for 10 (10) sec
    Thread: 5  Waiting
    process_alarm
    process_alarm
    thread_alarm
    Thread: 6  Slept for 5 (5) sec
    Thread: 6  Waiting
    process_alarm
    process_alarm
    
    ...
    thread_alarm
    Thread: 5  Slept for 0 (1) sec
    end