diff options
author | David Vrabel <david.vrabel@csr.com> | 2008-10-20 16:07:19 +0100 |
---|---|---|
committer | David Vrabel <david.vrabel@csr.com> | 2008-10-20 16:07:19 +0100 |
commit | 61e0e79ee3c609eb34edf2fe023708cba6a79b1f (patch) | |
tree | 663deacffd4071120dc9badb70428fe5f124c7b9 /Documentation/RCU/rcuref.txt | |
parent | c15895ef30c2c03e99802951787183039a349d32 (diff) | |
parent | 0cfd81031a26717fe14380d18275f8e217571615 (diff) |
Merge branch 'master' into for-upstream
Conflicts:
Documentation/ABI/testing/sysfs-bus-usb
drivers/Makefile
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); |