Patch Name:  PHKL_5689

Patch Description: s700 9.0[357] correct vfork panic or hang

Creation Date: 95/06/14

Post Date:  95/06/20

Hardware Platforms - OS Releases:
        s700: 9.03 9.05 9.07

Products: N/A

Filesets:
        KERN-BLD

Automatic Reboot?: Yes

Status: General Release

Critical:
        Yes
        PHKL_5689: HANG
        PHKL_4967: PANIC

Path Name:  /hp-ux_patches/s700/9.X/PHKL_5689

Symptoms:
        PHKL_5689:
        This patch fixes a defect in vfork; the defect causes the
        system to hang forever.

        PHKL_4967:
        panic: vfork_transfer entered in bad state

Defect Description:
        PHKL_5689:
        The problem is that the vfork path is holding a lock
        without good reason.  While the lock is held, a page
        fault occurs.  During the processing required to bring
        the page in, the system attempts to grab the same lock;
        this results in a deadlock.

        The problem is easily recognized in a stack trace
        containing vfork/copytopreg/vfault.

        Since the defect requires a page fault to occur at just
        the right time, this should only happen on systems with
        heavy paging activity.

        PHKL_4967:
        Reset p_vforkbuf before we could sleep in copytopreg. Else,
        we could sleep, the vforked child could exit, the parent
        would resume with a non-zero p_vforkbuf with VFORK_BAD.
        And then we'd panic with vfork_transfer entered in bad state

SR:
        1653108951 5003268995

Patch Files:  
        /etc/conf/libhp-ux.a(kern_fork.o)

what(1) Output:
        /etc/conf/libhp-ux.a(kern_fork.o):
                kern_fork.c   $Revision: 1.63.61.19 $ $Date: 95/06/1
                        4 08:54:33 $ PATCH_9.03 (PHKL_5689)

sum(1) Output:
        596 20 /etc/conf/libhp-ux.a(kern_fork.o)

Patch Conflicts: None

Patch Dependencies:  None

Hardware Dependencies:  None

Other Dependencies:  None

Supersedes:  
        PHKL_4967

Equivalent Patches: None

Patch Package Size:  60 Kbytes

Installation Instructions:  
        Please review all instructions and the Hewlett-Packard
        SupportLine User Guide or your Hewlett-Packard support terms
        and conditions for precautions, scope of license,
        restrictions, and, limitation of liability and warranties,
        before installing this patch.
        ------------------------------------------------------------
        1. Back up your system before installing a patch.

        2. Copy the patch to your /tmp directory and unshar it:

                cd /tmp
                cp patch_source/PHKL_5689 .
                sh PHKL_5689

        3. Become root and run update:

                /etc/update

        4. Use the cursor keys to select "Change Source or
           Destination ->" and press [Return].

        5. Select "From Tape Device to Local System ..."
           in the Change window and

        6. Change "Source: /dev/rmt/0m" to
           "Source: /tmp/PHKL_5689.updt"

        7. Press "Done" (f4).

        8. Follow the standard directions for update.

        Update moves the original software to
        /system/PHKL_5689/orig.  Keep this file to recover from any
        potential problems.  You should move the .text file to
        /system/PHKL_5689 for future reference.

        To put this patch on a magnetic tape and update from the
        tape drive, use dd:

                dd if=PHKL_5689.updt of=/dev/rmt/0m bs=2048

Special Installation Instructions:  None