Serial Console Hangs in Solaris

Sometimes the serial console becomes unresponsive on SunFire Systems. The ONLY thing that can be done to resolve this is to restart the system. Other fixes might be plugging in a keyboard. This is very frustrating for any type of remote maintenance because the serial console is also the ONLY method to console some SunFire's making remote resets nearly impossible unless someone reset the power via a UPS which would be a complete pain.

Here's a quote from the sun website available at: http://sunsolve.sun.com/search/document.do?assetkey=1-26-25589-1

-----START PASTE ------------
A "tip" serial port may hang and become unresponsive. When this occurs any commands used to access the port will not respond. This may result in having to reboot the system to regain access to the port.

2. Contributing Factors This problem can occur in the following releases:

SPARC

* Solaris 2.5.1
* Solaris 2.6
* Solaris 7
* Solaris 8

Intel

* Solaris 2.5.1
* Solaris 2.6
* Solaris 7
* Solaris 8

3. Symptoms When the described problem occurs the serial port becomes unresponsive. Regardless of what commands are used to access the port there will be no response. The processes can not be killed to regain access to the port.

Solution Summary Top
4. Relief/Workaround It might be possible to gain access to the port by disabling and then enabling the port monitor using the following command sequence: