diff options
author | Ingo Molnar <mingo@elte.hu> | 2008-10-12 12:49:27 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-10-12 12:49:27 +0200 |
commit | 1389ac4b976abdc0555280dfc1aa2c3abcc19641 (patch) | |
tree | 1ec51aa0b1e33201f6f4f3bebc657f9ec65f8539 /Documentation/RCU/rcuref.txt | |
parent | 69e13ad56f9e2cd81c4f8bfd6267211c10c14c08 (diff) | |
parent | fd048088306656824958e7783ffcee27e241b361 (diff) |
Merge branch 'linus' into x86/signal
Conflicts:
arch/x86/kernel/signal_64.c
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); |