Messages in this thread Patch in this message | | | From | Zygo Blaxell <> | Date | Fri, 12 Jun 2009 13:37:50 -0400 | Subject | [PATCH] LIB: remove unmatched write_lock() in gen_pool_destroy |
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Fix mismatch between calls to write_lock() and write_unlock() in gen_pool_destroy by removing the write_lock().
Signed-off-by: Zygo Blaxell <zygo.blaxell@xandros.com> --- There is a call to write_lock() in gen_pool_destroy which is not balanced by any corresponding write_unlock(). This causes problems with preemption because the preemption-disable counter is incremented in the write_lock() call, but never decremented by any call to write_unlock(). This bug is difficult to observe in the field because only two in-tree drivers call gen_pool_destroy, and one of them is non-x86 arch-specific code.
To fix this, I have chosen removing the write_lock() over adding a write_unlock() because the lock in question is inside a structure which is being freed. Any other thread that waited to acquire such a lock while gen_pool_destroy was running would find itself holding a lock in recently-freed or about-to-be-freed memory. This would result in memory corruption or a crash whether &pool->lock is held or not.
Using a pool while it is in the process of being destroyed is a bug that must be resolved outside of the gen_pool_destroy function.
lib/genalloc.c | 1 - 1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/lib/genalloc.c b/lib/genalloc.c index f6d276d..eed2bdb 100644 --- a/lib/genalloc.c +++ b/lib/genalloc.c @@ -85,7 +85,6 @@ void gen_pool_destroy(struct gen_pool *pool) int bit, end_bit; - write_lock(&pool->lock); list_for_each_safe(_chunk, _next_chunk, &pool->chunks) { chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk); list_del(&chunk->next_chunk); -- 1.5.6.5
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