Patch Name:  PHKL_5867

Patch Description: s700 10.00 fix for a process hang in semop(2)

Creation Date: 95/08/01

Post Date:  95/08/07

Hardware Platforms - OS Releases:
        s700: 10.00

Products: N/A

Filesets:
        OS-Core.CORE-KRN

Automatic Reboot?: Yes

Status: General Release

Critical: No

Path Name:  /hp-ux_patches/s700/10.X/PHKL_5867

Symptoms:
        PHKL_5867:
        A process that uses semop(2) may hang indefinitely.
        The bug only shows up if some other process also
        uses semop(2), specifically requesting two or more
        semaphore operations in a single call.

Defect Description:
        PHKL_5867:
        The symptom here is that a process may sleep forever,
        waiting on a semaphore that is available.

        The cause is that semop supports operations on multiple
        semaphores.  If the first semaphore is available, but the
        second one is not, semop must back out by releasing the
        first one before going to sleep on the second one.  The
        back out code calls semundo which does release the
        semaphore; however, it fails to do a wakeup which is
        necessary if some other process is waiting for that
        same semaphore.

        The fix was to modify the back out code so that it
        performs the necessary wakeup.

        This bug shows up in 10.0 because the semop code was
        redesigned to be more efficient by performing the absolute
        minimum number of wakeups necessary for correct
        functionality.  Obviously, we were too aggressive and
        forgot one of them.

SR:
        5003276675

Patch Files:
        /usr/conf/lib/libhp-ux.a(sysV_sem.o)

what(1) Output:
        /usr/conf/lib/libhp-ux.a(sysV_sem.o):
                sysV_sem.c  $Date: 95/07/31 10:33:02 $ $Revision: 1.
                        29.91.2 $ PATCH_10.0 (PHKL_5867)

cksum(1) Output:
        712612022 16656 /usr/conf/lib/libhp-ux.a(sysV_sem.o)

Patch Conflicts: None

Patch Dependencies:  None

Hardware Dependencies:  None

Other Dependencies:  None

Supersedes:  None

Equivalent Patches:
        PHKL_5868:
        s800: 10.00

        PHKL_5869:
        s700: 10.01

        PHKL_5870:
        s800: 10.01

Patch Package Size:  70 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. Login as root.

        3. Copy the patch to the /tmp directory.

        4. Move to the /tmp directory and unshar the patch:

                cd /tmp
                sh PHKL_5867

        5a. For a standalone system, run swinstall to install the
            patch:

                swinstall -x autoreboot=true -x match_target=true \
                        -s /tmp/PHKL_5867.depot

        5b. For a NFS Diskless cluster, run swcluster on the server
            to install the patch on the server and all clients:

                swcluster -x autoreboot=true \
                        -x mount_all_filesystems=true \
                        -s /tmp/PHKL_5867.depot PHKL_5867

        By default swinstall will archive the original software in
        /var/adm/sw/patch/PHKL_5867.  If you do not wish to retain a
        copy of the original software, you can create an empty file
        named /var/adm/sw/patch/PATCH_NOSAVE.

        Warning: If this file exists when a patch is installed, the
                 patch cannot be deinstalled.  Please be careful
                 when using this feature.

        It is recommended that you move the PHKL_5867.text file to
        /var/adm/sw/patch for future reference.

        To put this patch on a magnetic tape and install from the
        tape drive, use the command:

                swpackage -s /tmp/PHKL_5867.depot -x   \
                        target_type=tape -d /dev/rmt/0m PHKL_5867

Special Installation Instructions:  None