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2014-04-29documentation: Record rcu_dereference() value mishandlingPaul E. McKenney1-4/+8
Recent LKML discussings (see http://lwn.net/Articles/586838/ and http://lwn.net/Articles/588300/ for the LWN writeups) brought out some ways of misusing the return value from rcu_dereference() that are not necessarily completely intuitive. This commit therefore documents what can and cannot safely be done with these values. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2014-02-17documentation: Document call_rcu() safety mechanisms and limitationsPaul E. McKenney1-5/+13
The call_rcu() family of primitives will take action to accelerate grace periods when the number of callbacks pending on a given CPU becomes excessive. Although this safety mechanism can be useful, it is no substitute for users of call_rcu() having rate-limit controls in place. This commit adds this nuance to the documentation. Reported-by: "Michael S. Tsirkin" <mst@redhat.com> Reported-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2013-09-25rcu: Fix occurrence of "the the" in checklist.txtMichael Opdenacker1-2/+2
Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Add "then" as suggested by Josh Triplett. ] Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2013-06-10rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw().Paul E. McKenney1-6/+0
These interfaces never did get used, so this commit removes them, their rcutorture tests, and documentation referencing them. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2013-03-12rcu: Documentation updatePaul E. McKenney1-10/+16
This commit applies a few updates based on a quick review of the RCU documentations. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-11-13rcu: Remove list_for_each_continue_rcu()Paul E. McKenney1-9/+8
The list_for_each_continue_rcu() macro is no longer used, so this commit removes it. The list_for_each_entry_continue_rcu() macro should be used instead. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-09-23rcu: Document SRCU dead-CPU capabilities, emphasize read-side limitsPaul E. McKenney1-0/+6
The current documentation did not help someone grepping for SRCU to learn that disabling preemption is not a replacement for srcu_read_lock(), so upgrade the documentation to bring this out, not just for SRCU, but also for RCU-bh. Also document the fact that SRCU readers are respected on CPUs executing in user mode, idle CPUs, and even on offline CPUs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
2012-07-02rcu: Update documentation to cover call_srcu() and srcu_barrier().Paul E. McKenney1-19/+20
The advent of call_srcu() and srcu_barrier() obsoleted some of the documentation, so this commit brings that up to date. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-02-21rcu: Call out dangers of expedited RCU primitivesPaul E. McKenney1-0/+14
The expedited RCU primitives can be quite useful, but they have some high costs as well. This commit updates and creates docbook comments calling out the costs, and updates the RCU documentation as well. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11rcu: Add documentation for raw SRCU read-side primitivesPaul E. McKenney1-0/+6
Update various files in Documentation/RCU to reflect srcu_read_lock_raw() and srcu_read_unlock_raw(). Credit to Peter Zijlstra for suggesting use of the existing _raw suffix instead of the earlier bulkref names. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2010-08-20rcu: document ways of stalling updates in low-memory situationsPaul E. McKenney1-7/+16
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2010-08-19rcu: add shiny new debug assists to Documentation/RCU/checklist.txtPaul E. McKenney1-0/+23
Add a section describing PROVE_RCU, DEBUG_OBJECTS_RCU_HEAD, and the __rcu sparse checking to the RCU checklist. Suggested-by: David Miller <davem@davemloft.net> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2010-04-14rcu: Update docs for rcu_access_pointer and rcu_dereference_protectedPaul E. McKenney1-3/+4
Update examples and lists of APIs to include these new primitives. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com Cc: eric.dumazet@gmail.com LKML-Reference: <1270852752-25278-3-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-02-25rcu: Documentation update for CONFIG_PROVE_RCUPaul E. McKenney1-14/+20
Adds a lockdep.txt file and updates checklist.txt and whatisRCU.txt to reflect the new lockdep-enabled capabilities of RCU. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-13-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-16rcu: 1Q2010 update for RCU documentationPaul E. McKenney1-81/+119
Add expedited functions. Review documentation and update obsolete verbiage. Also fix the advice for the RCU CPU-stall kernel configuration parameter, and document RCU CPU-stall warnings. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <12635142581866-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-07-03rcu: Add synchronize_sched_expedited() rcutorture doc + updatesPaul E. McKenney1-5/+15
This patch updates the rcutorture documentation to include updated output format. It also brings the RCU documentation up to date. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Cc: davem@davemloft.net Cc: dada1@cosmosbay.com Cc: zbr@ioremap.net Cc: jeff.chua.linux@gmail.com Cc: paulus@samba.org Cc: laijs@cn.fujitsu.com Cc: jengelh@medozas.de Cc: r000n@r000n.net Cc: benh@kernel.crashing.org Cc: mathieu.desnoyers@polymtl.ca LKML-Reference: <12459460983193-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-10rcu: documentation 1Q09 updatePaul E. McKenney1-0/+12
Update the RCU documentation to call out the need for callers of primitives like call_rcu() and synchronize_rcu() to prevent subsequent RCU readers from hazard. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-08-15rcu: remove list_for_each_rcu()Paul E. McKenney1-1/+1
All of the in-tree uses of list_for_each_rcu() have been converted to list_for_each_entry_rcu(), so list_for_each_rcu() can now be removed. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-05-19sched: 1Q08 RCU doc update, add call_rcu_sched()Paul E. McKenney1-29/+60
Long-delayed update to the RCU documentation, including adding the new call_rcu_sched() and rcu_barrier_sched() APIs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2007-07-16Document the fact that RCU callbacks can run in parallelPaul E. McKenney1-1/+9
Add an item to the RCU documentation checklist noting that RCU callbacks can run in parallel. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2006-10-04[PATCH] srcu-3: RCU variant permitting read-side blockingPaul E. McKenney1-0/+38
Updated patch adding a variant of RCU that permits sleeping in read-side critical sections. SRCU is as follows: o Each use of SRCU creates its own srcu_struct, and each srcu_struct has its own set of grace periods. This is critical, as it prevents one subsystem with a blocking reader from holding up SRCU grace periods for other subsystems. o The SRCU primitives (srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu()) all take a pointer to a srcu_struct. o The SRCU primitives must be called from process context. o srcu_read_lock() returns an int that must be passed to the matching srcu_read_unlock(). Realtime RCU avoids the need for this by storing the state in the task struct, but SRCU needs to allow a given code path to pass through multiple SRCU domains -- storing state in the task struct would therefore require either arbitrary space in the task struct or arbitrary limits on SRCU nesting. So I kicked the state-storage problem up to the caller. Of course, it is not permitted to call synchronize_srcu() while in an SRCU read-side critical section. o There is no call_srcu(). It would not be hard to implement one, but it seems like too easy a way to OOM the system. (Hey, we have enough trouble with call_rcu(), which does -not- permit readers to sleep!!!) So, if you want it, please tell me why... [josht@us.ibm.com: sparse notation] Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com> Signed-off-by: Josh Triplett <josh@freedesktop.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-25[PATCH] RCU documentation: self-limiting updates and call_rcu()Paul E. McKenney1-3/+41
An update to the RCU documentation calling out the self-limiting-update-rate advantages of synchronize_rcu(), and describing how to use call_rcu() in a way that results in self-limiting updates. Self-limiting updates are important to avoiding RCU-induced OOM in face of denial-of-service attacks. Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-01[PATCH] RCU documentation fixes (January 2006 update)Paul E. McKenney1-0/+6
Updates to in-tree RCU documentation based on comments over the past few months. Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-10[PATCH] Yet another RCU documentation updatePaul E. McKenney1-11/+12
Update RCU documentation based on discussions and review of RCU-based tree patches. Add an introductory whatisRCU.txt file. Signed-off-by: <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-01[PATCH] Update RCU documentationPaul E. McKenney1-13/+34
Update the RCU documentation to allow for the new synchronize_rcu() and synchronize_sched() primitives. Fix a few other nits as well. Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-04-16Linux-2.6.12-rc2v2.6.12-rc2Linus Torvalds1-0/+157
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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