Re: [RESEND PATCH bpf-next 1/2] selftests/bpf: libarena: Add rbtree data structure

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Mon May 11, 2026 at 2:40 PM PDT, Emil Tsalapatis wrote:
> Add a native red-black tree data structure to libarena.
> The data structure supports multiple APIs (key-value based,
> node based) with which users can query and modify it. The
> tree uses the libarena memory allocator to manage its data.
>
> Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
> ---
>  .../bpf/libarena/include/libarena/rbtree.h    |   89 ++
>  .../bpf/libarena/selftests/st_rbtree.bpf.c    |  974 ++++++++++++++++

st_ is too obscure. Use test_ ?

> +SEC("syscall")
> +__weak int test_rbtree_insert_one(void)

None of these tests check parallel operations, right?
Let's add them and add the lock.
Not sure what's the point of lockless rbtree->freelist
when the whole thing still needs to be locked?

imo there is no point in single threaded primitives.
Only syscall prog can be single threaded. The rest run in parallel.

> +		arena_stderr("WARNING: Attempting to allocate a node "
> +				"for a NULL rbtree\n");

Don't split strings, since it's harder to grep for them.
It's ok that they're long and go over 80 or ever 100 chars.

> +__weak
> +int rb_print_pop_up(rbnode_t **rbnode, u8 *depthp, enum rb_print_state (*stack)[RB_MAXLVL_PRINT], enum rb_print_state *state)
> +{
> +	volatile u8 depth;
> +	int j;
> +
> +	if (unlikely(!rbnode || !depthp || !stack || !state))
> +		return -EINVAL;
> +
> +	WRITE_ONCE(depth, *depthp);

WRITE_ONCE? what for?