Under 2.2.14 and prior, I had problems with spin_lock dead-lock on Sparc SS-10 platforms equipped with quad Ross RTK-625 CPUs. Oddly, I did not have any problem with a 4/670MP with exactly the same CPU's (in fact I took the CPU modules out of an SS-10 and stuck them in a 4/670MP so they were the SAME modules). These were the 100mhz version. Under 2.2.15 the spin_lock dead-lock issue seems to have dissappeared, but now I see two new failures modes, and worse, these failure modes appears to affect single CPU machines as well. One failure mode, the machines will hang hard. No response to anything typed at the console, not even L1-A will work. The only way to get the machines to recover is to power cycle them. This affects both SS-10's with multiple Ross Hypersparc CPU's and LX's with a single TI CPU. The other failure mode is the machine will stop responding, you can't telnet/rlogin/ssh in, Apache won't response, etc. But whatever you type at the console is echoed and you can still switch virtual consoles. However, if you switch consoles and get a new login prompt and type a password, the password prompt never appears. You can continue to switch consoles and type things and see it echo but the machine continues not to respond. Control-Alt-Delete also does not work, but in this failure mode L1-A does work. Neither failure mode produces any console messages, no OOPS, no spin_lock deadlock errors, NADA, which needless to say doesn't make troubleshooting easy.