Patch Name: PHKL_28314

Patch Description: s700_800 11.00 PTHREAD_PROCESS_SHARED mutexes enhancement

Creation Date: 02/11/27

Post Date:  03/01/29

Hardware Platforms - OS Releases:
	s700: 11.00
	s800: 11.00

Products: N/A

Filesets:
	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_32,v=HP
	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_64,v=HP

Automatic Reboot?: Yes

Status: General Release

Critical:
	Yes
	PHKL_28314: HANG

Category Tags:
	defect_repair enhancement general_release critical
	halts_system

Path Name: /hp-ux_patches/s700_800/11.X/PHKL_28314

Symptoms:
	PHKL_28314:
	( SR:8606286053 CR:JAGae49995 )
	Applications using PTHREAD_PROCESS_SHARED mutexes hang on
	systems having installed all of PHKL_25998, PHKL_25999, and
	PHCO_26000 (or superceeding) patches.

	The application stack traces may be similar to:

	  __lwp_mutex_lock_sys+0010 (C0054B18)
	  __lwp_mutex_lock+003c (C0054624)
	  __pthread_mutex_lock+0270 (C004E08C)

	PHKL_25998:
	( SR:8606186056 CR:JAGad55261 )
	Software providers may observe performance deficiencies in
	applications which heavily use shared mutexes.  Performance
	of a PTHREAD_PROCESS_SHARED mutex unlock operation is slower
	than that of a PTHREAD_PROCESS_PRIVATE mutex, even in the
	non-contended (i.e., no waiters) case.

Defect Description:
	PHKL_28314:
	( SR:8606286053 CR:JAGae49995 )
	A race between the heavyweight and new lightweight shared
	mutex unlock system calls causes the mutex to be left in the
	locked state, even though the unlock function has completed.
	The waiters-update phase of the heavyweight path, if delayed
	due to interrupts occurring within a multi-word write
	sequence, can undo the work of a simultaneously occuring
	lightweight unlock.

	When this occurs, any further attempts by the application to
	lock the mutex will wait indefinitely, causing the
	application to hang.

	Resolution:
	Corrected waiters-update phase of heavyweight unlock system
	call to write a single word which does not interfere with
	the lightweight system call.  This closes the race, ensuring
	that work of a simultaneous lightweight unlock system call
	is not undone.

	PHKL_25998:
	( SR:8606186056 CR:JAGad55261 )
	In the PTHREAD_PROCESS_SHARED mutex case, the unlock
	operation always makes a system call to synchronize with
	threads in other processes which may be waiting for the
	mutex.  This makes the code path significantly longer.

	Resolution:
	Adapt the existing system call which handles waiters of
	shared mutexes to coordinate with a new light weight system
	call which handles shared mutex unlock.  (Patch PHKL_25999,
	also required for this enhancement, provides the new light
	weight system call for shared mutex unlock.  Patch
	PHCO_26000, also required for this enhancement, adapts the
	libpthread library to use the new light weight system call.)

Enhancement:
	No (superseded patches contained enhancements)
	PHKL_28314:
		Enhancements were delivered in a patch this one has
		superseded.  Please review the Defect Description
		text for more information.

SR:
	8606186056 8606286053

Patch Files:
	
	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_32,v=HP:
	/usr/conf/lib/libhp-ux.a(lwp_synch.o)

	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_64,v=HP:
	/usr/conf/lib/libhp-ux.a(lwp_synch.o)

what(1) Output:
	
	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_32,v=HP:
	/usr/conf/lib/libhp-ux.a(lwp_synch.o):
		lwp_synch.c $Date: 2002/11/27 11:27:58 $Revision: r1
			1ros/4 PATCH_11.00 (PHKL_28314)

	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_64,v=HP:
	/usr/conf/lib/libhp-ux.a(lwp_synch.o):
		lwp_synch.c $Date: 2002/11/27 11:27:58 $Revision: r1
			1ros/4 PATCH_11.00 (PHKL_28314)

cksum(1) Output:
	
	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_32,v=HP:
	2584622034 18376 /usr/conf/lib/libhp-ux.a(lwp_synch.o)

	OS-Core.CORE2-KRN,fr=B.11.00,fa=HP-UX_B.11.00_64,v=HP:
	2766731422 53008 /usr/conf/lib/libhp-ux.a(lwp_synch.o)

Patch Conflicts: None

Patch Dependencies: None

Hardware Dependencies: None

Other Dependencies:
	PHKL_25998:  To enable the pthread shared mutex performance
	enhancement, three patches (PHKL_25998, PHKL_25999, and
	PHCO_26000) are required.

Supersedes:
	PHKL_25998 

Equivalent Patches:
	PHKL_27315:
	s700: 11.11
	s800: 11.11

Patch Package Size: 100 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_28314

	5. Run swinstall to install the patch:

		swinstall -x autoreboot=true -x patch_match_target=true \
			  -s /tmp/PHKL_28314.depot

	By default swinstall will archive the original software in 
	/var/adm/sw/save/PHKL_28314.  If you do not wish to retain a
	copy of the original software, include the patch_save_files
	option in the swinstall command above:

		-x patch_save_files=false

	WARNING: If patch_save_files is false when a patch is installed,
		 the patch cannot be deinstalled.  Please be careful
		 when using this feature.

	For future reference, the contents of the PHKL_28314.text file is 
	available in the product readme:

		swlist -l product -a readme -d @ /tmp/PHKL_28314.depot

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

		dd if=/tmp/PHKL_28314.depot of=/dev/rmt/0m bs=2k

Special Installation Instructions: None