diff options
author | David Woodhouse <David.Woodhouse@intel.com> | 2008-10-13 17:13:56 +0100 |
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committer | David Woodhouse <David.Woodhouse@intel.com> | 2008-10-13 17:13:56 +0100 |
commit | e758936e02700ff88a0b08b722a3847b95283ef2 (patch) | |
tree | 50c919bef1b459a778b85159d5929de95b6c4a01 /Documentation/RCU/rcuref.txt | |
parent | 239cfbde1f5843c4a24199f117d5f67f637d72d5 (diff) | |
parent | 4480f15b3306f43bbb0310d461142b4e897ca45b (diff) |
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
Conflicts:
include/asm-x86/statfs.h
Diffstat (limited to 'Documentation/RCU/rcuref.txt')
-rw-r--r-- | Documentation/RCU/rcuref.txt | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/Documentation/RCU/rcuref.txt b/Documentation/RCU/rcuref.txt index 451de2ad832..4202ad09313 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); |