On Tue, Dec 18, 2018 at 12:03:34AM -0500, Zhu Yanjun wrote:
> In rxe_pool.c, pool state is protected by some read/write locks.
> Now these read/write locks are replaced with atomic bitops. This can
> make source code compact.
>
> Signed-off-by: Zhu Yanjun <yanjun.zhu@xxxxxxxxxx>
> drivers/infiniband/sw/rxe/rxe_pool.c | 22 +++++++---------------
> drivers/infiniband/sw/rxe/rxe_pool.h | 2 +-
> 2 files changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_pool.c b/drivers/infiniband/sw/rxe/rxe_pool.c
> index 36b53fb94a49..1a7efe0e3bb1 100644
> +++ b/drivers/infiniband/sw/rxe/rxe_pool.c
> @@ -222,7 +222,7 @@ int rxe_pool_init(
> pool->key_size = rxe_type_info[type].key_size;
> }
>
> - pool->state = RXE_POOL_STATE_VALID;
> + set_bit(RXE_POOL_STATE_VALID, &pool->state);
>
> out:
> return err;
> @@ -232,7 +232,7 @@ static void rxe_pool_release(struct kref *kref)
> {
> struct rxe_pool *pool = container_of(kref, struct rxe_pool, ref_cnt);
>
> - pool->state = RXE_POOL_STATE_INVALID;
> + set_bit(RXE_POOL_STATE_INVALID, &pool->state);
> kfree(pool->table);
> }
>
> @@ -243,14 +243,10 @@ static void rxe_pool_put(struct rxe_pool *pool)
>
> int rxe_pool_cleanup(struct rxe_pool *pool)
> {
> - unsigned long flags;
> -
> - write_lock_irqsave(&pool->pool_lock, flags);
> - pool->state = RXE_POOL_STATE_INVALID;
> + set_bit(RXE_POOL_STATE_INVALID, &pool->state);
> if (atomic_read(&pool->num_elem) > 0)
> pr_warn("%s pool destroyed with unfree'd elem\n",
> pool_name(pool));
> - write_unlock_irqrestore(&pool->pool_lock, flags);
>
> rxe_pool_put(pool);
>
> @@ -380,17 +376,13 @@ void rxe_drop_index(void *arg)
> void *rxe_alloc(struct rxe_pool *pool)
> {
> struct rxe_pool_entry *elem;
> - unsigned long flags;
>
> might_sleep_if(!(pool->flags & RXE_POOL_ATOMIC));
>
> - read_lock_irqsave(&pool->pool_lock, flags);
> - if (pool->state != RXE_POOL_STATE_VALID) {
> - read_unlock_irqrestore(&pool->pool_lock, flags);
> + if (!test_bit(RXE_POOL_STATE_VALID, &pool->state))
> return NULL;
> - }
> +
> kref_get(&pool->ref_cnt);
> - read_unlock_irqrestore(&pool->pool_lock, flags);
I doubt this locking can be removed without creating races between
pool_state and the kref_get.
I suspect the locking, refcounting, and lifetime in this pool code is
just all wrong. If you fix that then the pool->state probably just
goes away completely.
Good code usually does't have racy coding patterns like the above at
least..
Jason
