Comments about RTS threads:

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

They use old version of a lot of 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 already written. Se mysys/my_pthread.c for more info.

At least the following should be changed:

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

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

The biggest unsolved problem is the following:

To get thread_level alarms I changed mysys/thr_alarm.c to wait between alarms with pthread_cond_timedwait() but this aborts with error EINTR. I tried to debug the thread library 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 -DHAVE_rts_threads.
• Compile thr_alarm
• If there is some small differences in the implementation they may be fixed by changing my_pthread.h and my_pthread.c
• Run thr_alarm. If it runs without any 'warning', 'error' or aborted messages you are one the right track. Here follows an successful run on Solaris:

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

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