Documentation/RCU/RTFP.txt - kernel/msm - Gitiles

 Read the F-ing Papers!


 This document describes RCU-related publications, and is followed by
 the corresponding bibtex entries.  A number of the publications may
 be found at http://www.rdrop.com/users/paulmck/RCU/.

 The first thing resembling RCU was published in 1980, when Kung and Lehman
 [Kung80] recommended use of a garbage collector to defer destruction
 of nodes in a parallel binary search tree in order to simplify its
 implementation.  This works well in environments that have garbage
 collectors, but current production garbage collectors incur significant
 read-side overhead.

 In 1982, Manber and Ladner [Manber82,Manber84] recommended deferring
 destruction until all threads running at that time have terminated, again
 for a parallel binary search tree.  This approach works well in systems
 with short-lived threads, such as the K42 research operating system.
 However, Linux has long-lived tasks, so more is needed.

 In 1986, Hennessy, Osisek, and Seigh [Hennessy89] introduced passive
 serialization, which is an RCU-like mechanism that relies on the presence
 of "quiescent states" in the VM/XA hypervisor that are guaranteed not
 to be referencing the data structure.  However, this mechanism was not
 optimized for modern computer systems, which is not surprising given
 that these overheads were not so expensive in the mid-80s.  Nonetheless,
 passive serialization appears to be the first deferred-destruction
 mechanism to be used in production.  Furthermore, the relevant patent has
 lapsed, so this approach may be used in non-GPL software, if desired.
 (In contrast, use of RCU is permitted only in software licensed under
 GPL.  Sorry!!!)

 In 1990, Pugh [Pugh90] noted that explicitly tracking which threads
 were reading a given data structure permitted deferred free to operate
 in the presence of non-terminating threads.  However, this explicit
 tracking imposes significant read-side overhead, which is undesirable
 in read-mostly situations.  This algorithm does take pains to avoid
 write-side contention and parallelize the other write-side overheads by
 providing a fine-grained locking design, however, it would be interesting
 to see how much of the performance advantage reported in 1990 remains
 in 2004.

 At about this same time, Adams [Adams91] described ``chaotic relaxation'',
 where the normal barriers between successive iterations of convergent
 numerical algorithms are relaxed, so that iteration $n$ might use
 data from iteration $n-1$ or even $n-2$.  This introduces error,
 which typically slows convergence and thus increases the number of
 iterations required.  However, this increase is sometimes more than made
 up for by a reduction in the number of expensive barrier operations,
 which are otherwise required to synchronize the threads at the end
 of each iteration.  Unfortunately, chaotic relaxation requires highly
 structured data, such as the matrices used in scientific programs, and
 is thus inapplicable to most data structures in operating-system kernels.

 In 1993, Jacobson [Jacobson93] verbally described what is perhaps the
 simplest deferred-free technique: simply waiting a fixed amount of time
 before freeing blocks awaiting deferred free.  Jacobson did not describe
 any write-side changes he might have made in this work using SGI's Irix
 kernel.  Aju John published a similar technique in 1995 [AjuJohn95].
 This works well if there is a well-defined upper bound on the length of
 time that reading threads can hold references, as there might well be in
 hard real-time systems.  However, if this time is exceeded, perhaps due
 to preemption, excessive interrupts, or larger-than-anticipated load,
 memory corruption can ensue, with no reasonable means of diagnosis.
 Jacobson's technique is therefore inappropriate for use in production
 operating-system kernels, except when such kernels can provide hard
 real-time response guarantees for all operations.

 Also in 1995, Pu et al. [Pu95a] applied a technique similar to that of Pugh's
 read-side-tracking to permit replugging of algorithms within a commercial
 Unix operating system.  However, this replugging permitted only a single
 reader at a time.  The following year, this same group of researchers
 extended their technique to allow for multiple readers [Cowan96a].
 Their approach requires memory barriers (and thus pipeline stalls),
 but reduces memory latency, contention, and locking overheads.

 1995 also saw the first publication of DYNIX/ptx's RCU mechanism
 [Slingwine95], which was optimized for modern CPU architectures,
 and was successfully applied to a number of situations within the
 DYNIX/ptx kernel.  The corresponding conference paper appeared in 1998
 [McKenney98].

 In 1999, the Tornado and K42 groups described their "generations"
 mechanism, which quite similar to RCU [Gamsa99].  These operating systems
 made pervasive use of RCU in place of "existence locks", which greatly
 simplifies locking hierarchies.

 2001 saw the first RCU presentation involving Linux [McKenney01a]
 at OLS.  The resulting abundance of RCU patches was presented the
 following year [McKenney02a], and use of RCU in dcache was first
 described that same year [Linder02a].

 Also in 2002, Michael [Michael02b,Michael02a] presented "hazard-pointer"
 techniques that defer the destruction of data structures to simplify
 non-blocking synchronization (wait-free synchronization, lock-free
 synchronization, and obstruction-free synchronization are all examples of
 non-blocking synchronization).  In particular, this technique eliminates
 locking, reduces contention, reduces memory latency for readers, and
 parallelizes pipeline stalls and memory latency for writers.  However,
 these techniques still impose significant read-side overhead in the
 form of memory barriers.  Researchers at Sun worked along similar lines
 in the same timeframe [HerlihyLM02,HerlihyLMS03].  These techniques
 can be thought of as inside-out reference counts, where the count is
 represented by the number of hazard pointers referencing a given data
 structure (rather than the more conventional counter field within the
 data structure itself).

 In 2003, the K42 group described how RCU could be used to create
 hot-pluggable implementations of operating-system functions.  Later that
 year saw a paper describing an RCU implementation of System V IPC
 [Arcangeli03], and an introduction to RCU in Linux Journal [McKenney03a].

 2004 has seen a Linux-Journal article on use of RCU in dcache
 [McKenney04a], a performance comparison of locking to RCU on several
 different CPUs [McKenney04b], a dissertation describing use of RCU in a
 number of operating-system kernels [PaulEdwardMcKenneyPhD], a paper
 describing how to make RCU safe for soft-realtime applications [Sarma04c],
 and a paper describing SELinux performance with RCU [JamesMorris04b].

 2005 has seen further adaptation of RCU to realtime use, permitting
 preemption of RCU realtime critical sections [PaulMcKenney05a,
 PaulMcKenney05b].

 Bibtex Entries

 @article{Kung80
 ,author="H. T. Kung and Q. Lehman"
 ,title="Concurrent Maintenance of Binary Search Trees"
 ,Year="1980"
 ,Month="September"
 ,journal="ACM Transactions on Database Systems"
 ,volume="5"
 ,number="3"
 ,pages="354-382"
 }

 @techreport{Manber82
 ,author="Udi Manber and Richard E. Ladner"
 ,title="Concurrency Control in a Dynamic Search Structure"
 ,institution="Department of Computer Science, University of Washington"
 ,address="Seattle, Washington"
 ,year="1982"
 ,number="82-01-01"
 ,month="January"
 ,pages="28"
 }

 @article{Manber84
 ,author="Udi Manber and Richard E. Ladner"
 ,title="Concurrency Control in a Dynamic Search Structure"
 ,Year="1984"
 ,Month="September"
 ,journal="ACM Transactions on Database Systems"
 ,volume="9"
 ,number="3"
 ,pages="439-455"
 }

 @techreport{Hennessy89
 ,author="James P. Hennessy and Damian L. Osisek and Joseph W. {Seigh II}"
 ,title="Passive Serialization in a Multitasking Environment"
 ,institution="US Patent and Trademark Office"
 ,address="Washington, DC"
 ,year="1989"
 ,number="US Patent 4,809,168 (lapsed)"
 ,month="February"
 ,pages="11"
 }

 @techreport{Pugh90
 ,author="William Pugh"
 ,title="Concurrent Maintenance of Skip Lists"
 ,institution="Institute of Advanced Computer Science Studies, Department of Computer Science, University of Maryland"
 ,address="College Park, Maryland"
 ,year="1990"
 ,number="CS-TR-2222.1"
 ,month="June"
 }

 @Book{Adams91
 ,Author="Gregory R. Adams"
 ,title="Concurrent Programming, Principles, and Practices"
 ,Publisher="Benjamin Cummins"
 ,Year="1991"
 }

 @unpublished{Jacobson93
 ,author="Van Jacobson"
 ,title="Avoid Read-Side Locking Via Delayed Free"
 ,year="1993"
 ,month="September"
 ,note="Verbal discussion"
 }

 @Conference{AjuJohn95
 ,Author="Aju John"
 ,Title="Dynamic vnodes -- Design and Implementation"
 ,Booktitle="{USENIX Winter 1995}"
 ,Publisher="USENIX Association"
 ,Month="January"
 ,Year="1995"
 ,pages="11-23"
 ,Address="New Orleans, LA"
 }

 @techreport{Slingwine95
 ,author="John D. Slingwine and Paul E. McKenney"
 ,title="Apparatus and Method for Achieving Reduced Overhead Mutual
 Exclusion and Maintaining Coherency in a Multiprocessor System
 Utilizing Execution History and Thread Monitoring"
 ,institution="US Patent and Trademark Office"
 ,address="Washington, DC"
 ,year="1995"
 ,number="US Patent 5,442,758 (contributed under GPL)"
 ,month="August"
 }

 @techreport{Slingwine97
 ,author="John D. Slingwine and Paul E. McKenney"
 ,title="Method for maintaining data coherency using thread
 activity summaries in a multicomputer system"
 ,institution="US Patent and Trademark Office"
 ,address="Washington, DC"
 ,year="1997"
 ,number="US Patent 5,608,893 (contributed under GPL)"
 ,month="March"
 }

 @techreport{Slingwine98
 ,author="John D. Slingwine and Paul E. McKenney"
 ,title="Apparatus and method for achieving reduced overhead
 mutual exclusion and maintaining coherency in a multiprocessor
 system utilizing execution history and thread monitoring"
 ,institution="US Patent and Trademark Office"
 ,address="Washington, DC"
 ,year="1998"
 ,number="US Patent 5,727,209 (contributed under GPL)"
 ,month="March"
 }

 @Conference{McKenney98
 ,Author="Paul E. McKenney and John D. Slingwine"
 ,Title="Read-Copy Update: Using Execution History to Solve Concurrency
 Problems"
 ,Booktitle="{Parallel and Distributed Computing and Systems}"
 ,Month="October"
 ,Year="1998"
 ,pages="509-518"
 ,Address="Las Vegas, NV"
 }

 @Conference{Gamsa99
 ,Author="Ben Gamsa and Orran Krieger and Jonathan Appavoo and Michael Stumm"
 ,Title="Tornado: Maximizing Locality and Concurrency in a Shared Memory
 Multiprocessor Operating System"
 ,Booktitle="{Proceedings of the 3\textsuperscript{rd} Symposium on
 Operating System Design and Implementation}"
 ,Month="February"
 ,Year="1999"
 ,pages="87-100"
 ,Address="New Orleans, LA"
 }

 @techreport{Slingwine01
 ,author="John D. Slingwine and Paul E. McKenney"
 ,title="Apparatus and method for achieving reduced overhead
 mutual exclusion and maintaining coherency in a multiprocessor
 system utilizing execution history and thread monitoring"
 ,institution="US Patent and Trademark Office"
 ,address="Washington, DC"
 ,year="2001"
 ,number="US Patent 5,219,690 (contributed under GPL)"
 ,month="April"
 }

 @Conference{McKenney01a
 ,Author="Paul E. McKenney and Jonathan Appavoo and Andi Kleen and
 Orran Krieger and Rusty Russell and Dipankar Sarma and Maneesh Soni"
 ,Title="Read-Copy Update"
 ,Booktitle="{Ottawa Linux Symposium}"
 ,Month="July"
 ,Year="2001"
 ,note="Available:
 \url{http://www.linuxsymposium.org/2001/abstracts/readcopy.php}
 \url{http://www.rdrop.com/users/paulmck/rclock/rclock_OLS.2001.05.01c.pdf}
 [Viewed June 23, 2004]"
 annotation="
 Described RCU, and presented some patches implementing and using it in
 the Linux kernel.
 "
 }

 @Conference{Linder02a
 ,Author="Hanna Linder and Dipankar Sarma and Maneesh Soni"
 ,Title="Scalability of the Directory Entry Cache"
 ,Booktitle="{Ottawa Linux Symposium}"
 ,Month="June"
 ,Year="2002"
 ,pages="289-300"
 }

 @Conference{McKenney02a
 ,Author="Paul E. McKenney and Dipankar Sarma and
 Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell"
 ,Title="Read-Copy Update"
 ,Booktitle="{Ottawa Linux Symposium}"
 ,Month="June"
 ,Year="2002"
 ,pages="338-367"
 ,note="Available:
 \url{http://www.linux.org.uk/~ajh/ols2002_proceedings.pdf.gz}
 [Viewed June 23, 2004]"
 }

 @article{Appavoo03a
 ,author="J. Appavoo and K. Hui and C. A. N. Soules and R. W. Wisniewski and
 D. M. {Da Silva} and O. Krieger and M. A. Auslander and D. J. Edelsohn and
 B. Gamsa and G. R. Ganger and P. McKenney and M. Ostrowski and
 B. Rosenburg and M. Stumm and J. Xenidis"
 ,title="Enabling Autonomic Behavior in Systems Software With Hot Swapping"
 ,Year="2003"
 ,Month="January"
 ,journal="IBM Systems Journal"
 ,volume="42"
 ,number="1"
 ,pages="60-76"
 }

 @Conference{Arcangeli03
 ,Author="Andrea Arcangeli and Mingming Cao and Paul E. McKenney and
 Dipankar Sarma"
 ,Title="Using Read-Copy Update Techniques for {System V IPC} in the
 {Linux} 2.5 Kernel"
 ,Booktitle="Proceedings of the 2003 USENIX Annual Technical Conference
 (FREENIX Track)"
 ,Publisher="USENIX Association"
 ,year="2003"
 ,month="June"
 ,pages="297-310"
 }

 @article{McKenney03a
 ,author="Paul E. McKenney"
 ,title="Using {RCU} in the {Linux} 2.5 Kernel"
 ,Year="2003"
 ,Month="October"
 ,journal="Linux Journal"
 ,volume="1"
 ,number="114"
 ,pages="18-26"
 }

 @techreport{Friedberg03a
 ,author="Stuart A. Friedberg"
 ,title="Lock-Free Wild Card Search Data Structure and Method"
 ,institution="US Patent and Trademark Office"
 ,address="Washington, DC"
 ,year="2003"
 ,number="US Patent 6,662,184 (contributed under GPL)"
 ,month="December"
 ,pages="112"
 }

 @article{McKenney04a
 ,author="Paul E. McKenney and Dipankar Sarma and Maneesh Soni"
 ,title="Scaling dcache with {RCU}"
 ,Year="2004"
 ,Month="January"
 ,journal="Linux Journal"
 ,volume="1"
 ,number="118"
 ,pages="38-46"
 }

 @Conference{McKenney04b
 ,Author="Paul E. McKenney"
 ,Title="{RCU} vs. Locking Performance on Different {CPUs}"
 ,Booktitle="{linux.conf.au}"
 ,Month="January"
 ,Year="2004"
 ,Address="Adelaide, Australia"
 ,note="Available:
 \url{http://www.linux.org.au/conf/2004/abstracts.html#90}
 \url{http://www.rdrop.com/users/paulmck/rclock/lockperf.2004.01.17a.pdf}
 [Viewed June 23, 2004]"
 }

 @phdthesis{PaulEdwardMcKenneyPhD
 ,author="Paul E. McKenney"
 ,title="Exploiting Deferred Destruction:
 An Analysis of Read-Copy-Update Techniques
 in Operating System Kernels"
 ,school="OGI School of Science and Engineering at
 Oregon Health and Sciences University"
 ,year="2004"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/RCUdissertation.2004.07.14e1.pdf}
 [Viewed October 15, 2004]"
 }

 @Conference{Sarma04c
 ,Author="Dipankar Sarma and Paul E. McKenney"
 ,Title="Making RCU Safe for Deep Sub-Millisecond Response Realtime Applications"
 ,Booktitle="Proceedings of the 2004 USENIX Annual Technical Conference
 (FREENIX Track)"
 ,Publisher="USENIX Association"
 ,year="2004"
 ,month="June"
 ,pages="182-191"
 }

 @unpublished{JamesMorris04b
 ,Author="James Morris"
 ,Title="Recent Developments in {SELinux} Kernel Performance"
 ,month="December"
 ,year="2004"
 ,note="Available:
 \url{http://www.livejournal.com/users/james_morris/2153.html}
 [Viewed December 10, 2004]"
 }

 @unpublished{PaulMcKenney05a
 ,Author="Paul E. McKenney"
 ,Title="{[RFC]} {RCU} and {CONFIG\_PREEMPT\_RT} progress"
 ,month="May"
 ,year="2005"
 ,note="Available:
 \url{http://lkml.org/lkml/2005/5/9/185}
 [Viewed May 13, 2005]"
 ,annotation="
 	First publication of working lock-based deferred free patches
 	for the CONFIG_PREEMPT_RT environment.
 "
 }

 @conference{PaulMcKenney05b
 ,Author="Paul E. McKenney and Dipankar Sarma"
 ,Title="Towards Hard Realtime Response from the Linux Kernel on SMP Hardware"
 ,Booktitle="linux.conf.au 2005"
 ,month="April"
 ,year="2005"
 ,address="Canberra, Australia"
 ,note="Available:
 \url{http://www.rdrop.com/users/paulmck/RCU/realtimeRCU.2005.04.23a.pdf}
 [Viewed May 13, 2005]"
 ,annotation="
 	Realtime turns into making RCU yet more realtime friendly.
 "
 }
	Read the F-ing Papers!


	This document describes RCU-related publications, and is followed by
	the corresponding bibtex entries. A number of the publications may
	be found at http://www.rdrop.com/users/paulmck/RCU/.

	The first thing resembling RCU was published in 1980, when Kung and Lehman
	[Kung80] recommended use of a garbage collector to defer destruction
	of nodes in a parallel binary search tree in order to simplify its
	implementation. This works well in environments that have garbage
	collectors, but current production garbage collectors incur significant
	read-side overhead.

	In 1982, Manber and Ladner [Manber82,Manber84] recommended deferring
	destruction until all threads running at that time have terminated, again
	for a parallel binary search tree. This approach works well in systems
	with short-lived threads, such as the K42 research operating system.
	However, Linux has long-lived tasks, so more is needed.

	In 1986, Hennessy, Osisek, and Seigh [Hennessy89] introduced passive
	serialization, which is an RCU-like mechanism that relies on the presence
	of "quiescent states" in the VM/XA hypervisor that are guaranteed not
	to be referencing the data structure. However, this mechanism was not
	optimized for modern computer systems, which is not surprising given
	that these overheads were not so expensive in the mid-80s. Nonetheless,
	passive serialization appears to be the first deferred-destruction
	mechanism to be used in production. Furthermore, the relevant patent has
	lapsed, so this approach may be used in non-GPL software, if desired.
	(In contrast, use of RCU is permitted only in software licensed under
	GPL. Sorry!!!)

	In 1990, Pugh [Pugh90] noted that explicitly tracking which threads
	were reading a given data structure permitted deferred free to operate
	in the presence of non-terminating threads. However, this explicit
	tracking imposes significant read-side overhead, which is undesirable
	in read-mostly situations. This algorithm does take pains to avoid
	write-side contention and parallelize the other write-side overheads by
	providing a fine-grained locking design, however, it would be interesting
	to see how much of the performance advantage reported in 1990 remains
	in 2004.

	At about this same time, Adams [Adams91] described ``chaotic relaxation'',
	where the normal barriers between successive iterations of convergent
	numerical algorithms are relaxed, so that iteration $n$ might use
	data from iteration $n-1$ or even $n-2$. This introduces error,
	which typically slows convergence and thus increases the number of
	iterations required. However, this increase is sometimes more than made
	up for by a reduction in the number of expensive barrier operations,
	which are otherwise required to synchronize the threads at the end
	of each iteration. Unfortunately, chaotic relaxation requires highly
	structured data, such as the matrices used in scientific programs, and
	is thus inapplicable to most data structures in operating-system kernels.

	In 1993, Jacobson [Jacobson93] verbally described what is perhaps the
	simplest deferred-free technique: simply waiting a fixed amount of time
	before freeing blocks awaiting deferred free. Jacobson did not describe
	any write-side changes he might have made in this work using SGI's Irix
	kernel. Aju John published a similar technique in 1995 [AjuJohn95].
	This works well if there is a well-defined upper bound on the length of
	time that reading threads can hold references, as there might well be in
	hard real-time systems. However, if this time is exceeded, perhaps due
	to preemption, excessive interrupts, or larger-than-anticipated load,
	memory corruption can ensue, with no reasonable means of diagnosis.
	Jacobson's technique is therefore inappropriate for use in production
	operating-system kernels, except when such kernels can provide hard
	real-time response guarantees for all operations.

	Also in 1995, Pu et al. [Pu95a] applied a technique similar to that of Pugh's
	read-side-tracking to permit replugging of algorithms within a commercial
	Unix operating system. However, this replugging permitted only a single
	reader at a time. The following year, this same group of researchers
	extended their technique to allow for multiple readers [Cowan96a].
	Their approach requires memory barriers (and thus pipeline stalls),
	but reduces memory latency, contention, and locking overheads.

	1995 also saw the first publication of DYNIX/ptx's RCU mechanism
	[Slingwine95], which was optimized for modern CPU architectures,
	and was successfully applied to a number of situations within the
	DYNIX/ptx kernel. The corresponding conference paper appeared in 1998
	[McKenney98].

	In 1999, the Tornado and K42 groups described their "generations"
	mechanism, which quite similar to RCU [Gamsa99]. These operating systems
	made pervasive use of RCU in place of "existence locks", which greatly
	simplifies locking hierarchies.

	2001 saw the first RCU presentation involving Linux [McKenney01a]
	at OLS. The resulting abundance of RCU patches was presented the
	following year [McKenney02a], and use of RCU in dcache was first
	described that same year [Linder02a].

	Also in 2002, Michael [Michael02b,Michael02a] presented "hazard-pointer"
	techniques that defer the destruction of data structures to simplify
	non-blocking synchronization (wait-free synchronization, lock-free
	synchronization, and obstruction-free synchronization are all examples of
	non-blocking synchronization). In particular, this technique eliminates
	locking, reduces contention, reduces memory latency for readers, and
	parallelizes pipeline stalls and memory latency for writers. However,
	these techniques still impose significant read-side overhead in the
	form of memory barriers. Researchers at Sun worked along similar lines
	in the same timeframe [HerlihyLM02,HerlihyLMS03]. These techniques
	can be thought of as inside-out reference counts, where the count is
	represented by the number of hazard pointers referencing a given data
	structure (rather than the more conventional counter field within the
	data structure itself).

	In 2003, the K42 group described how RCU could be used to create
	hot-pluggable implementations of operating-system functions. Later that
	year saw a paper describing an RCU implementation of System V IPC
	[Arcangeli03], and an introduction to RCU in Linux Journal [McKenney03a].

	2004 has seen a Linux-Journal article on use of RCU in dcache
	[McKenney04a], a performance comparison of locking to RCU on several
	different CPUs [McKenney04b], a dissertation describing use of RCU in a
	number of operating-system kernels [PaulEdwardMcKenneyPhD], a paper
	describing how to make RCU safe for soft-realtime applications [Sarma04c],
	and a paper describing SELinux performance with RCU [JamesMorris04b].

	2005 has seen further adaptation of RCU to realtime use, permitting
	preemption of RCU realtime critical sections [PaulMcKenney05a,
	PaulMcKenney05b].

	Bibtex Entries

	@article{Kung80
	,author="H. T. Kung and Q. Lehman"
	,title="Concurrent Maintenance of Binary Search Trees"
	,Year="1980"
	,Month="September"
	,journal="ACM Transactions on Database Systems"
	,volume="5"
	,number="3"
	,pages="354-382"
	}

	@techreport{Manber82
	,author="Udi Manber and Richard E. Ladner"
	,title="Concurrency Control in a Dynamic Search Structure"
	,institution="Department of Computer Science, University of Washington"
	,address="Seattle, Washington"
	,year="1982"
	,number="82-01-01"
	,month="January"
	,pages="28"
	}

	@article{Manber84
	,author="Udi Manber and Richard E. Ladner"
	,title="Concurrency Control in a Dynamic Search Structure"
	,Year="1984"
	,Month="September"
	,journal="ACM Transactions on Database Systems"
	,volume="9"
	,number="3"
	,pages="439-455"
	}

	@techreport{Hennessy89
	,author="James P. Hennessy and Damian L. Osisek and Joseph W. {Seigh II}"
	,title="Passive Serialization in a Multitasking Environment"
	,institution="US Patent and Trademark Office"
	,address="Washington, DC"
	,year="1989"
	,number="US Patent 4,809,168 (lapsed)"
	,month="February"
	,pages="11"
	}

	@techreport{Pugh90
	,author="William Pugh"
	,title="Concurrent Maintenance of Skip Lists"
	,institution="Institute of Advanced Computer Science Studies, Department of Computer Science, University of Maryland"
	,address="College Park, Maryland"
	,year="1990"
	,number="CS-TR-2222.1"
	,month="June"
	}

	@Book{Adams91
	,Author="Gregory R. Adams"
	,title="Concurrent Programming, Principles, and Practices"
	,Publisher="Benjamin Cummins"
	,Year="1991"
	}

	@unpublished{Jacobson93
	,author="Van Jacobson"
	,title="Avoid Read-Side Locking Via Delayed Free"
	,year="1993"
	,month="September"
	,note="Verbal discussion"
	}

	@Conference{AjuJohn95
	,Author="Aju John"
	,Title="Dynamic vnodes -- Design and Implementation"
	,Booktitle="{USENIX Winter 1995}"
	,Publisher="USENIX Association"
	,Month="January"
	,Year="1995"
	,pages="11-23"
	,Address="New Orleans, LA"
	}

	@techreport{Slingwine95
	,author="John D. Slingwine and Paul E. McKenney"
	,title="Apparatus and Method for Achieving Reduced Overhead Mutual
	Exclusion and Maintaining Coherency in a Multiprocessor System
	Utilizing Execution History and Thread Monitoring"
	,institution="US Patent and Trademark Office"
	,address="Washington, DC"
	,year="1995"
	,number="US Patent 5,442,758 (contributed under GPL)"
	,month="August"
	}

	@techreport{Slingwine97
	,author="John D. Slingwine and Paul E. McKenney"
	,title="Method for maintaining data coherency using thread
	activity summaries in a multicomputer system"
	,institution="US Patent and Trademark Office"
	,address="Washington, DC"
	,year="1997"
	,number="US Patent 5,608,893 (contributed under GPL)"
	,month="March"
	}

	@techreport{Slingwine98
	,author="John D. Slingwine and Paul E. McKenney"
	,title="Apparatus and method for achieving reduced overhead
	mutual exclusion and maintaining coherency in a multiprocessor
	system utilizing execution history and thread monitoring"
	,institution="US Patent and Trademark Office"
	,address="Washington, DC"
	,year="1998"
	,number="US Patent 5,727,209 (contributed under GPL)"
	,month="March"
	}

	@Conference{McKenney98
	,Author="Paul E. McKenney and John D. Slingwine"
	,Title="Read-Copy Update: Using Execution History to Solve Concurrency
	Problems"
	,Booktitle="{Parallel and Distributed Computing and Systems}"
	,Month="October"
	,Year="1998"
	,pages="509-518"
	,Address="Las Vegas, NV"
	}

	@Conference{Gamsa99
	,Author="Ben Gamsa and Orran Krieger and Jonathan Appavoo and Michael Stumm"
	,Title="Tornado: Maximizing Locality and Concurrency in a Shared Memory
	Multiprocessor Operating System"
	,Booktitle="{Proceedings of the 3\textsuperscript{rd} Symposium on
	Operating System Design and Implementation}"
	,Month="February"
	,Year="1999"
	,pages="87-100"
	,Address="New Orleans, LA"
	}

	@techreport{Slingwine01
	,author="John D. Slingwine and Paul E. McKenney"
	,title="Apparatus and method for achieving reduced overhead
	mutual exclusion and maintaining coherency in a multiprocessor
	system utilizing execution history and thread monitoring"
	,institution="US Patent and Trademark Office"
	,address="Washington, DC"
	,year="2001"
	,number="US Patent 5,219,690 (contributed under GPL)"
	,month="April"
	}

	@Conference{McKenney01a
	,Author="Paul E. McKenney and Jonathan Appavoo and Andi Kleen and
	Orran Krieger and Rusty Russell and Dipankar Sarma and Maneesh Soni"
	,Title="Read-Copy Update"
	,Booktitle="{Ottawa Linux Symposium}"
	,Month="July"
	,Year="2001"
	,note="Available:
	\url{http://www.linuxsymposium.org/2001/abstracts/readcopy.php}
	\url{http://www.rdrop.com/users/paulmck/rclock/rclock_OLS.2001.05.01c.pdf}
	[Viewed June 23, 2004]"
	annotation="
	Described RCU, and presented some patches implementing and using it in
	the Linux kernel.
	"
	}

	@Conference{Linder02a
	,Author="Hanna Linder and Dipankar Sarma and Maneesh Soni"
	,Title="Scalability of the Directory Entry Cache"
	,Booktitle="{Ottawa Linux Symposium}"
	,Month="June"
	,Year="2002"
	,pages="289-300"
	}

	@Conference{McKenney02a
	,Author="Paul E. McKenney and Dipankar Sarma and
	Andrea Arcangeli and Andi Kleen and Orran Krieger and Rusty Russell"
	,Title="Read-Copy Update"
	,Booktitle="{Ottawa Linux Symposium}"
	,Month="June"
	,Year="2002"
	,pages="338-367"
	,note="Available:
	\url{http://www.linux.org.uk/~ajh/ols2002_proceedings.pdf.gz}
	[Viewed June 23, 2004]"
	}

	@article{Appavoo03a
	,author="J. Appavoo and K. Hui and C. A. N. Soules and R. W. Wisniewski and
	D. M. {Da Silva} and O. Krieger and M. A. Auslander and D. J. Edelsohn and
	B. Gamsa and G. R. Ganger and P. McKenney and M. Ostrowski and
	B. Rosenburg and M. Stumm and J. Xenidis"
	,title="Enabling Autonomic Behavior in Systems Software With Hot Swapping"
	,Year="2003"
	,Month="January"
	,journal="IBM Systems Journal"
	,volume="42"
	,number="1"
	,pages="60-76"
	}

	@Conference{Arcangeli03
	,Author="Andrea Arcangeli and Mingming Cao and Paul E. McKenney and
	Dipankar Sarma"
	,Title="Using Read-Copy Update Techniques for {System V IPC} in the
	{Linux} 2.5 Kernel"
	,Booktitle="Proceedings of the 2003 USENIX Annual Technical Conference
	(FREENIX Track)"
	,Publisher="USENIX Association"
	,year="2003"
	,month="June"
	,pages="297-310"
	}

	@article{McKenney03a
	,author="Paul E. McKenney"
	,title="Using {RCU} in the {Linux} 2.5 Kernel"
	,Year="2003"
	,Month="October"
	,journal="Linux Journal"
	,volume="1"
	,number="114"
	,pages="18-26"
	}

	@techreport{Friedberg03a
	,author="Stuart A. Friedberg"
	,title="Lock-Free Wild Card Search Data Structure and Method"
	,institution="US Patent and Trademark Office"
	,address="Washington, DC"
	,year="2003"
	,number="US Patent 6,662,184 (contributed under GPL)"
	,month="December"
	,pages="112"
	}

	@article{McKenney04a
	,author="Paul E. McKenney and Dipankar Sarma and Maneesh Soni"
	,title="Scaling dcache with {RCU}"
	,Year="2004"
	,Month="January"
	,journal="Linux Journal"
	,volume="1"
	,number="118"
	,pages="38-46"
	}

	@Conference{McKenney04b
	,Author="Paul E. McKenney"
	,Title="{RCU} vs. Locking Performance on Different {CPUs}"
	,Booktitle="{linux.conf.au}"
	,Month="January"
	,Year="2004"
	,Address="Adelaide, Australia"
	,note="Available:
	\url{http://www.linux.org.au/conf/2004/abstracts.html#90}
	\url{http://www.rdrop.com/users/paulmck/rclock/lockperf.2004.01.17a.pdf}
	[Viewed June 23, 2004]"
	}

	@phdthesis{PaulEdwardMcKenneyPhD
	,author="Paul E. McKenney"
	,title="Exploiting Deferred Destruction:
	An Analysis of Read-Copy-Update Techniques
	in Operating System Kernels"
	,school="OGI School of Science and Engineering at
	Oregon Health and Sciences University"
	,year="2004"
	,note="Available:
	\url{http://www.rdrop.com/users/paulmck/RCU/RCUdissertation.2004.07.14e1.pdf}
	[Viewed October 15, 2004]"
	}

	@Conference{Sarma04c
	,Author="Dipankar Sarma and Paul E. McKenney"
	,Title="Making RCU Safe for Deep Sub-Millisecond Response Realtime Applications"
	,Booktitle="Proceedings of the 2004 USENIX Annual Technical Conference
	(FREENIX Track)"
	,Publisher="USENIX Association"
	,year="2004"
	,month="June"
	,pages="182-191"
	}

	@unpublished{JamesMorris04b
	,Author="James Morris"
	,Title="Recent Developments in {SELinux} Kernel Performance"
	,month="December"
	,year="2004"
	,note="Available:
	\url{http://www.livejournal.com/users/james_morris/2153.html}
	[Viewed December 10, 2004]"
	}

	@unpublished{PaulMcKenney05a
	,Author="Paul E. McKenney"
	,Title="{[RFC]} {RCU} and {CONFIG\_PREEMPT\_RT} progress"
	,month="May"
	,year="2005"
	,note="Available:
	\url{http://lkml.org/lkml/2005/5/9/185}
	[Viewed May 13, 2005]"
	,annotation="
	First publication of working lock-based deferred free patches
	for the CONFIG_PREEMPT_RT environment.
	"
	}

	@conference{PaulMcKenney05b
	,Author="Paul E. McKenney and Dipankar Sarma"
	,Title="Towards Hard Realtime Response from the Linux Kernel on SMP Hardware"
	,Booktitle="linux.conf.au 2005"
	,month="April"
	,year="2005"
	,address="Canberra, Australia"
	,note="Available:
	\url{http://www.rdrop.com/users/paulmck/RCU/realtimeRCU.2005.04.23a.pdf}
	[Viewed May 13, 2005]"
	,annotation="
	Realtime turns into making RCU yet more realtime friendly.
	"
	}