SCSI_CAM-UNX CLCMC313_E1 SCSI CAM Layered Components ECO Summary

TITLE: SCSI_CAM-UNX CLCMC313_E1 SCSI CAM Layered Components ECO Summary
 

Copyright (c) Compaq Computer Corporation 1999.  All rights reserved.

Modification Date:  29-NOV-99
Modification Type:  New Kit

PRODUCT:    SCSI CAM (Common Access Method) Layered Components
            for Tru64 UNIX Version 3.1b or later

OP/SYS:     Tru64 UNIX Versions 4.0d, 4.0e, 4.0f, 4.0g

COMPONENT:  SCSI CAM Medium Changer Device Driver (cam_changer)

SOURCE:     Compaq Computer Corporation

ECO INFORMATION:

     ECO Kit Name:  CLCMC313_E1
     ECO Kits Superseded by This ECO Kit:  None
     ECO Kit Approximate Size:  320 Blocks
                             163840 Bytes

     Kit Applies To:  SCSI CAM Layered Components for Tru64 UNIX V3.1b
                      on Tru64 UNIX V4.0d, V4.0e, V4.0f, V4.0g
     System/Cluster Reboot Necessary:  No
     Rolling Re-boot Supported:  Information Not Available
     Installation Rating:  INSTALL_UNKNOWN


ECO KIT SUMMARY:

An ECO kit exists for cam_changer.o from SCSI CAM Layered Components for
Tru64 UNIX V3.1b or later on Tru64 UNIX V4.0d through V4.0g.  This kit
addresses the following problems: 

Problems Addressed in CLCMC313_E1:

System Panic when accessing media changer device.

This patch contains fixes for two problems with the changer driver.

 1)  Panic in changer_ready()

     During an open of the changer device, there was a window of
     opportunity in which another process could come in and start another
     open to the same device.  With multiple opens occurring
     simultaneously, one of the processes will close the device before
     the other.  When the close of the first process occurs, certain
     kernel data structures are cleared, which are still required for the
     other process which has the device open.  The next time the process
     which still has the device open, goes to access those kernel data
     structures, the system panics because of a NULL pointer. 

     Solution:

     The locking flag which is used to prevent other processes from
     opening the device at the same time has been expanded to include the
     entire open code, not just a small part of it, thereby closing the
     window during which another process can open the device while the
     first open is in progress. 

 2)  Panic in changer_read_attributes()

     When an attempt is made to open a changer device which has been
     disconnected, a structure member is not initialized properly. 

     Solution:

     A pointer is copied from one structure to another, which allows the
     changer_read_attributes() routine to succeed. 


INSTALLATION NOTES:

The patch provided is for V4.0D, V4.0E, V4.0F, and V4.0G systems.

The tar file contains the file cam_changer.4.0D.o.

This file should be installed on the customer's system in:

     /usr/opt/CLCXXX/mc

The symbolic link in that directory should point to this new patch,
replacing the symbolic link which previously existed. 

The kernel should then be rebuilt and the system rebooted.


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clcmc313_e1.README
clcmc313_e1.CHKSUM
clcmc313_e1.CVRLET_TXT
clcmc313_e1.tar
clcmc313_e1.CVRLET_TXT