Patch Name: PHKL_19907

Patch Description: s700 10.20 Improve perf for TLB purges, avoid MP hangs

Creation Date: 99/09/16

Post Date:  99/09/22

Hardware Platforms - OS Releases:
	s700: 10.20

Products: N/A

Filesets:
	OS-Core.CORE-KRN

Automatic Reboot?: Yes

Status: General Superseded

Critical:
	Yes
	PHKL_19907: HANG

Path Name: /hp-ux_patches/s700/10.X/PHKL_19907

Symptoms:
	PHKL_19907:
	In rare cases, systems would hang, with two processors
	stuck on the same innocuous-looking write instruction.
	Due to the timing in the spinlock deadlock code,
	processors may appear to be waiting on spinlocks which
	show up as free in panic dumps.

	PHKL_17653:
	On 2.0 Architecture systems, TLB purge instructions are
	purging more pages than necessary.  This does not cause
	the system to operate improperly, but it may have a
	slight negative impact on system performance.

Defect Description:
	PHKL_19907:
	There was a race condition where two processors could end
	up deadlocking while trying to update the same TLB entry.
	The deadlock was caused by an "in-progress" bit that was
	set when it should have been clear.
	Resolution:
	Clear the "in progress" bit so processors don't get stuck
	re-trying an update that was in fact successful.

	PHKL_17653:
	The problem lies with the PITLB and PDTLB instructions used
	in the 2.0 trap handlers.  The 2.0 architecture was
	enhanced to define that the low-order 4 bits of the
	address that is being purged specifies a "page size"
	(which is defined in Table 3-1 of the PA-RISC 2.0
	Architecture book by Gerry Kane).  However, the 2.0
	trap handlers only need to purge one page, and they do
	not zero the low-order 4 bits of the address that they
	wish to purge (the address that is used is the actual
	address that caused the trap).  This results in many
	more pages being purged than was intended.
	Resolution:
	The code now zero's the low-order 4 bits of the address.

SR:
	4701401646 4701426783

Patch Files:
	/usr/conf/lib/libhp-ux.a(asm_tlb2_0.o)

what(1) Output:
	/usr/conf/lib/libhp-ux.a(asm_tlb2_0.o):
		asm_tlb2_0.s      $Date: 99/09/16 11:09:30 $ $Revisi
			on: 1.3.98.8 $ PATCH_10.20 (PHKL_19907)

cksum(1) Output:
	3169412744 15376 /usr/conf/lib/libhp-ux.a(asm_tlb2_0.o)

Patch Conflicts: None

Patch Dependencies: None

Hardware Dependencies: None

Other Dependencies: None

Supersedes:
	PHKL_17653

Equivalent Patches:
	PHKL_19908:
	s800: 10.20

Patch Package Size: 80 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_19907

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

		swinstall -x autoreboot=true -x match_target=true \
			-s /tmp/PHKL_19907.depot

	By default swinstall will archive the original software in
	/var/adm/sw/patch/PHKL_19907.  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_19907.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:

		dd if=/tmp/PHKL_19907.depot of=/dev/rmt/0m bs=2k

Special Installation Instructions: None