If you follow the MIDAS documentation for setting up password protection, you will get strange messages:
[local:testexpt:S]/>passwd <---- setup a password
Password: <---- enter correct password here
ss_semaphore_wait_for: semop/semtimedop(21135376) returned -1, errno 22 (Invalid argument)
ss_semaphore_release: semop/semtimedop(21135376) returned -1, errno 22 (Invalid argument)
[local:testexpt:S]/>ss_semaphore_wait_for: semop/semtimedop(21037069) returned -1, errno 43 (Identifier removed)
The same messages will appear from all other programs - mhttpd, etc. They will be printed about every 1 second.
So what do they mean? They mean what they say - the semaphore is not there, it is easy to check using "ipcs" that semaphores with
those ids do not exist. In fact all the semaphores are missing (the ODB semaphore is eventually recreated, so at least ODB works
In this situation, MIDAS will not work correctly.
What is happening?
- cm_connect_experiment1() creates all the semaphores and remembers them in cm_set_experiment_semaphore()
- calls cm_set_client_info()
- cm_set_client_info() finds ODB /expt/sec/password, and returns CM_WRONG_PASSWORD
- before returning, it calls db_close_all_databases() and bm_close_all_buffers(), which delete all semaphores (put a print statement in
ss_semaphore_delete() to see this).
- (values saved by cm_set_experiment_semaphore() are stale now).
- (if by luck you have other midas programs still running, the semaphores will not be deleted)
- we are back to cm_connect_experiment1() which will ask for the password, call cm_set_client_info() again and continue as usual
- it will reopen ODB, recreating the ODB semaphore
- (but all the other semaphores are still deleted and values saved by cm_set_experiment_semaphore() are stale)
I through to improve this by fixing a bug in cm_msg_log() (where the messages are coming from) - it tries to lock the "MSG"
semaphore, but even if it could not lock it, it continues as usual and even calls an unlock at the end. (very bad). For catastrophic
locking failures like this (semaphore is deleted), we usually abort. But if I abort here, I get completely locked out from odb - odbedit
crashes right away and there is no way to do any corrective action other than delete odb and reload it from an xml file.
I know that some experiments use this password protection - why/how does it work there?
I think they are okey because they put critical programs like odbedit, mserver, mlogger and mhttpd into "/expt/sec/allowed
programs". In this case the pass the password check in cm_set_client_info() and the semaphores are not deleted. If any subsequent
program asks for the password, the semaphores survive because mlogger or mhttpd is already running and keeps semaphores from
What a mess.