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author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-10-10 13:10:51 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-10-10 13:10:51 -0700 |
commit | b922df7383749a1c0b7ea64c50fa839263d3816b (patch) | |
tree | dd72306ac173753649eb049d6d2734f4e2b95ff6 /Documentation | |
parent | c54dcd8ec9f05c8951d1e622e90904aef95379f9 (diff) | |
parent | cdbb92b31d3c465aa96bd09f2d42c39b87b32bee (diff) | |
download | kernel_samsung_smdk4412-b922df7383749a1c0b7ea64c50fa839263d3816b.zip kernel_samsung_smdk4412-b922df7383749a1c0b7ea64c50fa839263d3816b.tar.gz kernel_samsung_smdk4412-b922df7383749a1c0b7ea64c50fa839263d3816b.tar.bz2 |
Merge branch 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (21 commits)
rcu: RCU-based detection of stalled CPUs for Classic RCU, fix
rcu: RCU-based detection of stalled CPUs for Classic RCU
rcu: add rcu_read_lock_sched() / rcu_read_unlock_sched()
rcu: fix sparse shadowed variable warning
doc/RCU: fix pseudocode in rcuref.txt
rcuclassic: fix compiler warning
rcu: use irq-safe locks
rcuclassic: fix compilation NG
rcu: fix locking cleanup fallout
rcu: remove redundant ACCESS_ONCE definition from rcupreempt.c
rcu: fix classic RCU locking cleanup lockdep problem
rcu: trace fix possible mem-leak
rcu: just rename call_rcu_bh instead of making it a macro
rcu: remove list_for_each_rcu()
rcu: fixes to include/linux/rcupreempt.h
rcu: classic RCU locking and memory-barrier cleanups
rcu: prevent console flood when one CPU sees another AWOL via RCU
rcu, debug: detect stalled grace periods, cleanups
rcu, debug: detect stalled grace periods
rcu classic: new algorithm for callbacks-processing(v2)
...
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/RCU/checklist.txt | 2 | ||||
-rw-r--r-- | Documentation/RCU/rcuref.txt | 16 | ||||
-rw-r--r-- | Documentation/RCU/whatisRCU.txt | 2 |
3 files changed, 9 insertions, 11 deletions
diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt index cf5562c..6e25340 100644 --- a/Documentation/RCU/checklist.txt +++ b/Documentation/RCU/checklist.txt @@ -210,7 +210,7 @@ over a rather long period of time, but improvements are always welcome! number of updates per grace period. 9. All RCU list-traversal primitives, which include - rcu_dereference(), list_for_each_rcu(), list_for_each_entry_rcu(), + rcu_dereference(), list_for_each_entry_rcu(), list_for_each_continue_rcu(), and list_for_each_safe_rcu(), must be either within an RCU read-side critical section or must be protected by appropriate update-side locks. RCU diff --git a/Documentation/RCU/rcuref.txt b/Documentation/RCU/rcuref.txt index 451de2a..4202ad0 100644 --- a/Documentation/RCU/rcuref.txt +++ b/Documentation/RCU/rcuref.txt @@ -29,9 +29,9 @@ release_referenced() delete() } If this list/array is made lock free using RCU as in changing the -write_lock() in add() and delete() to spin_lock and changing read_lock -in search_and_reference to rcu_read_lock(), the atomic_get in -search_and_reference could potentially hold reference to an element which +write_lock() in add() and delete() to spin_lock() and changing read_lock() +in search_and_reference() to rcu_read_lock(), the atomic_inc() in +search_and_reference() could potentially hold reference to an element which has already been deleted from the list/array. Use atomic_inc_not_zero() in this scenario as follows: @@ -40,20 +40,20 @@ add() search_and_reference() { { alloc_object rcu_read_lock(); ... search_for_element - atomic_set(&el->rc, 1); if (atomic_inc_not_zero(&el->rc)) { - write_lock(&list_lock); rcu_read_unlock(); + atomic_set(&el->rc, 1); if (!atomic_inc_not_zero(&el->rc)) { + spin_lock(&list_lock); rcu_read_unlock(); return FAIL; add_element } ... ... - write_unlock(&list_lock); rcu_read_unlock(); + spin_unlock(&list_lock); rcu_read_unlock(); } } 3. 4. release_referenced() delete() { { - ... write_lock(&list_lock); + ... spin_lock(&list_lock); if (atomic_dec_and_test(&el->rc)) ... call_rcu(&el->head, el_free); delete_element - ... write_unlock(&list_lock); + ... spin_unlock(&list_lock); } ... if (atomic_dec_and_test(&el->rc)) call_rcu(&el->head, el_free); diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index e04d643..9617082 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -786,8 +786,6 @@ RCU pointer/list traversal: list_for_each_entry_rcu hlist_for_each_entry_rcu - list_for_each_rcu (to be deprecated in favor of - list_for_each_entry_rcu) list_for_each_continue_rcu (to be deprecated in favor of new list_for_each_entry_continue_rcu) |