Re: Re: NUMCPU >1 = IEE331A EXCESSIVE DISABLED SPIN LOOP DETECTED

On May 20, 2010, at 9:25 AM, Mike Stramba wrote:

> ..Except for  the  the "spin" messages, it was spewing, which I had  
> no idea what they meant ;)
>

Certain "locks" within MVS are so-called "suspend" locks (LOCAL LOCK,  
e.g.) whereas other locks within MVS are so-called "spin" locks  
(CHANNEL LOCK, e.g.).

There is only one "spin" lock within MVS which is not part of the  
LOCKing system, and that is the disabled lock within IEWFETCH, which  
is utilized to ensure that at least 240 bytes of the CONTROL/RLD  
record has been read, when FETCH is reading such records, as the  
relocation function which FETCH performs is done in a DIE, in  
response to a PCI interrupt issued by the channel when the READ  
CONTROL/RLD CCW was fetched by the channel.

The DIE "spins" on a byte within the CONTROL/RLD record, and when  
that byte changes, the DIE knows that the channel has actually read  
the CONTROL/RLD record, and it is safe for the data within that  
record to be processed.