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SubjectRe: [PATCH v2 1/3] io_uring: register single issuer task at creation
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On 9/26/22 18:09, Dylan Yudaken wrote:
> Instead of picking the task from the first submitter task, rather use the
> creator task or in the case of disabled (IORING_SETUP_R_DISABLED) the
> enabling task.
>
> This approach allows a lot of simplification of the logic here. This
> removes init logic from the submission path, which can always be a bit
> confusing, but also removes the need for locking to write (or read) the
> submitter_task.
>
> Users that want to move a ring before submitting can create the ring
> disabled and then enable it on the submitting task.

I think Dylan briefly mentioned before that it might be a good
idea to task limit registration as well. I can't think of a use
case at the moment but I agree we may find some in the future.


diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 242d896c00f3..60a471e43fd9 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3706,6 +3706,9 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
if (WARN_ON_ONCE(percpu_ref_is_dying(&ctx->refs)))
return -ENXIO;

+ if (ctx->submitter_task && ctx->submitter_task != current)
+ return -EEXIST;
+
if (ctx->restricted) {
if (opcode >= IORING_REGISTER_LAST)
return -EINVAL;

--
Pavel Begunkov

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