New subject: [Kamailio-Users] R: Fast lock loop with arm

24 Mar 2010

Hi,
I have a big problem with fast lock mutex on arm CPU: 
sometimes I find one or more children that go in an infinite loop, in the while loop of
get_lock function. 
They remain in Run for long time (sometimes hours) and openser keeps 100% CPU.

Now I have changed the functions get_lock and tsl in order to obtain more info and 
I observe that  (if and) when the process finish the cycle, it have done a big amount of
cycles.  

This the log with my added info:
Mar 26 20:29:08 SAM-IP openser[1645]: NOTICE:tm:_lock: ret 1 (cycle)
Mar 26 20:29:51 SAM-IP openser[1645]: NOTICE:tm:_lock: ret 1 (cycle)
Mar 26 20:29:55 SAM-IP openser[1645]: NOTICE:tm:_lock: ret 1 (cycle)

Mar 26 20:29:55 SAM-IP openser[1645]: NOTICE:tm:t_retransmit_reply: MYTM lock 
[process in loop]
Mar 26 20:33:46 SAM-IP openser[1645]: NOTICE:tm:_lock: ret 59374917 (cycle)
[after 4 minutes and 59374917 cycles, this is an example with a "short" loop]
Mar 26 20:33:46 SAM-IP openser[1645]: NOTICE:tm:t_retransmit_reply: MYTM lock done 

I'm not able to recognize the call flow that generates the loop (I know only that it
always happens when t_retransmit_reply calls LOCK_REPLIES), 
but I urgently need a work around to escape from the loop.

This is the get_lock function with my counter j:

inline static int get_lock(fl_lock_t* lock)
{
#ifdef ADAPTIVE_WAIT
	int i=ADAPTIVE_WAIT_LOOPS;
	int j=1;					/***** my change ****/
#endif

	while(tsl(lock)){
#ifdef BUSY_WAIT
#elif defined ADAPTIVE_WAIT
		j++;				/***** my change ****/
		if (i>0) i--;
		else sched_yield();
#else
		sched_yield();
#endif
	}
	return(j);
}

Can I break the lock when my counter reaches a big value? 
Should I call the unlock function after the break?
which value can be considered too big?

Thanks,
Daniele 

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[Kamailio-Users] Fast lock loop with arm