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* rcu: Replace list_first_entry_rcu() with list_first_or_null_rcu()Michel Machado2012-04-241-4/+29
| | | | | | | | | | | | | | | | | | | | | | | | | The list_first_entry_rcu() macro is inherently unsafe because it cannot be applied to an empty list. But because RCU readers do not exclude updaters, a list might become empty between the time that list_empty() claimed it was non-empty and the time that list_first_entry_rcu() is invoked. Therefore, the list_empty() test cannot be separated from the list_first_entry_rcu() call. This commit therefore combines these to macros to create a new list_first_or_null_rcu() macro that replaces the old (and unsafe) list_first_entry_rcu() macro. This patch incorporates Paul's review comments on the previous version of this patch available here: https://lkml.org/lkml/2012/4/2/536 This patch cannot break any upstream code because list_first_entry_rcu() is not being used anywhere in the kernel (tested with grep(1)), and any external code using it is probably broken as a result of using it. Signed-off-by: Michel Machado <michel@digirati.com.br> CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> CC: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: List-debug variants of rcu list routines.Dave Jones2012-04-241-1/+6
| | | | | | | | | | | | | | * Make __list_add_rcu check the next->prev and prev->next pointers just like __list_add does. * Make list_del_rcu use __list_del_entry, which does the same checking at deletion time. Has been running for a week here without anything being tripped up, but it seems worth adding for completeness just in case something ever does corrupt those lists. Signed-off-by: Dave Jones <davej@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Fix wrong check in list_splice_init_rcu()Jan H. Schönherr2011-07-201-1/+1
| | | | | | | | | | | If the list to be spliced is empty, then list_splice_init_rcu() has nothing to do. Unfortunately, list_splice_init_rcu() does not check the list to be spliced; it instead checks the list to be spliced into. This results in memory leaks given current usage. This commit therefore fixes the empty-list check. Signed-off-by: Jan H. Schönherr <schnhrr@cs.tu-berlin.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* list: remove prefetching from regular list iteratorsLinus Torvalds2011-05-191-3/+3
| | | | | | | | | | | | | | | | | | | | This is removes the use of software prefetching from the regular list iterators. We don't want it. If you do want to prefetch in some iterator of yours, go right ahead. Just don't expect the iterator to do it, since normally the downsides are bigger than the upsides. It also replaces <linux/prefetch.h> with <linux/const.h>, because the use of LIST_POISON ends up needing it. <linux/poison.h> is sadly not self-contained, and including prefetch.h just happened to hide that. Suggested by David Miller (networking has a lot of regular lists that are often empty or a single entry, and prefetching is not going to do anything but add useless instructions). Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: David S. Miller <davem@davemloft.net> Cc: linux-arch@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* hlist: remove software prefetching in hlist iteratorsLinus Torvalds2011-05-191-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | They not only increase the code footprint, they actually make things slower rather than faster. On internationally acclaimed benchmarks ("make -j16" on an already fully built kernel source tree) the hlist prefetching slows down the build by up to 1%. (Almost all of it comes from hlist_for_each_entry_rcu() as used by avc_has_perm_noaudit(), which is very hot due to all the pathname lookups to see if there is anything to do). The cause seems to be two-fold: - on at least some Intel cores, prefetch(NULL) ends up with some microarchitectural stall due to the TLB miss that it incurs. The hlist case triggers this very commonly, since the NULL pointer is the last entry in the list. - the prefetch appears to cause more D$ activity, probably because it prefetches hash list entries that are never actually used (because we ended the search early due to a hit). Regardless, the numbers clearly say that the implicit prefetching is simply a bad idea. If some _particular_ user of the hlist iterators wants to prefetch the next list entry, they can do so themselves explicitly, rather than depend on all list iterators doing so implicitly. Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: David S. Miller <davem@davemloft.net> Cc: linux-arch@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* rcu: remove unused __list_for_each_rcu() macroPaul E. McKenney2010-12-171-5/+0
| | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rculist: fix borked __list_for_each_rcu() macroMariusz Kozlowski2010-12-171-1/+1
| | | | | | | This restores parentheses blance. Signed-off-by: Mariusz Kozlowski <mk@lab.zgora.pl> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: add comment stating that list_empty() applies to RCU-protected listsPaul E. McKenney2010-08-201-0/+9
| | | | | | | | | | | Because list_empty() does not dereference any RCU-protected pointers, and further does not pass such pointers to the caller (so that the caller does not dereference them either), it is safe to use list_empty() on RCU-protected lists. There is no need for a list_empty_rcu(). This commit adds a comment stating this explicitly. Requested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rculist: avoid __rcu annotationsArnd Bergmann2010-08-191-19/+34
| | | | | | | | | | | | | | | | This avoids warnings from missing __rcu annotations in the rculist implementation, making it possible to use the same lists in both RCU and non-RCU cases. We can add rculist annotations later, together with lockdep support for rculist, which is missing as well, but that may involve changing all the users. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* net: rcu fixesEric Dumazet2010-05-031-0/+29
| | | | | | | | | | | Add hlist_for_each_entry_rcu_bh() and hlist_for_each_entry_continue_rcu_bh() macros, and use them in ipv6_get_ifaddr(), if6_get_first() and if6_get_next() to fix lockdeps warnings. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Reviewed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* IPv6: convert addrconf hash list to RCUstephen hemminger2010-03-201-0/+13
| | | | | | | | | | | Convert from reader/writer lock to RCU and spinlock for addrconf hash list. Adds an additional helper macro for hlist_for_each_entry_continue_rcu to handle the continue case. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* Merge branch 'master' of /home/davem/src/GIT/linux-2.6/David S. Miller2010-02-281-7/+7
|\ | | | | | | | | Conflicts: drivers/firmware/iscsi_ibft.c
| * rcu: Disable lockdep checking in RCU list-traversal primitivesPaul E. McKenney2010-02-251-7/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The theory is that use of bare rcu_dereference() is more prone to error than use of the RCU list-traversal primitives. Therefore, disable lockdep RCU read-side critical-section checking in these primitives for the time being. Once all of the rcu_dereference() uses have been dealt with, it may be time to re-enable lockdep checking for the RCU list-traversal 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 LKML-Reference: <1266887105-1528-4-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | seq_file: add RCU versions of new hlist/list iterators (v3)stephen hemminger2010-02-221-0/+5
|/ | | | | | | | Many usages of seq_file use RCU protected lists, so non RCU iterators will not work safely. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* netdev: add netdev_continue_rcustephen hemminger2009-11-101-0/+14
| | | | | | | | | This adds an RCU macro for continuing search, useful for some network devices like vlan. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* rculist.h: introduce list_entry_rcu() and list_first_entry_rcu()Jiri Pirko2009-04-141-2/+28
| | | | | | | | | | | | | | I've run into the situation where I need to use list_first_entry with rcu-guarded list. This patch introduces this. Also simplify list_for_each_entry_rcu() to use new list_entry_rcu() instead of list_entry(). Signed-off-by: Jiri Pirko <jpirko@redhat.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: dipankar@in.ibm.com LKML-Reference: <20090414153356.GC3999@psychotron.englab.brq.redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* rcu: remove list_for_each_rcu()Paul E. McKenney2008-08-151-14/+0
| | | | | | | | 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>
* mmu-notifiers: add list_del_init_rcu()Andrea Arcangeli2008-07-281-0/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Introduce list_del_init_rcu() and document it. Signed-off-by: Andrea Arcangeli <andrea@qumranet.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Jack Steiner <steiner@sgi.com> Cc: Robin Holt <holt@sgi.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Kanoj Sarcar <kanojsarcar@yahoo.com> Cc: Roland Dreier <rdreier@cisco.com> Cc: Steve Wise <swise@opengridcomputing.com> Cc: Avi Kivity <avi@qumranet.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Anthony Liguori <aliguori@us.ibm.com> Cc: Chris Wright <chrisw@redhat.com> Cc: Marcelo Tosatti <marcelo@kvack.org> Cc: Eric Dumazet <dada1@cosmosbay.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Izik Eidus <izike@qumranet.com> Cc: Anthony Liguori <aliguori@us.ibm.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* RCU, rculist.h: fix list iteratorsPaul E. McKenney2008-05-191-33/+15
| | | | | | | | | RCU list iterators: should prefetch ever be optimised out with no side-effects, the current version will lose the barrier completely. Pointed-out-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* rculist.h: use the rcu APIFranck Bui-Huu2008-05-191-14/+9
| | | | | | | | | | | | Make almost all list mutation primitives use rcu_assign_pointer(). The main point of this being readability improvement. Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Josh Triplett <josh@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* rcu: split list.h and move rcu-protected lists into rculist.hFranck Bui-Huu2008-05-191-0/+396
Move rcu-protected lists from list.h into a new header file rculist.h. This is done because list are a very used primitive structure all over the kernel and it's currently impossible to include other header files in this list.h without creating some circular dependencies. For example, list.h implements rcu-protected list and uses rcu_dereference() without including rcupdate.h. It actually compiles because users of rcu_dereference() are macros. Others RCU functions could be used too but aren't probably because of this. Therefore this patch creates rculist.h which includes rcupdates without to many changes/troubles. Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Josh Triplett <josh@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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