Re: [PATCH v2] io_uring: protect remaining lockless ctx->rings accesses with RCU

[Jens Axboe <axboe@kernel.dk>]

On 3/31/26 11:24 PM, junxi qian wrote:
> Hi Jens,
> 
> The kernel test robot reported sparse warnings on your commit (9d0a7bda72c5):
> 
> io_uring/wait.c:309:49: sparse: cast removes address space '__rcu' of expression
> io_uring/wait.c:319:16: sparse: cast removes address space '__rcu' of expression
> io_uring/wait.c:319:54: sparse: cast removes address space '__rcu' of expression
> 
> The issue is that wait.c lines 309 and 319 access ctx->rings_rcu directly
> without going through rcu_dereference(), which sparse flags as an __rcu
> address space violation.
> 
> The fix would be to replace the raw ctx->rings_rcu dereferences with
> io_get_rings(ctx), e.g.:
> 
> READ_ONCE(ctx->rings_rcu->cq.tail)
> 
> READ_ONCE(io_get_rings(ctx)->cq.tail)
> 
> Apologies for not catching this during my review of v2.

Indeed, might just fold that in. It's just a sparse complaint, but might
as well get it sorted before it goes upstream.

-- 
Jens Axboe