Re: [PATCH for-next 04/12] io_uring: reschedule retargeting at shutdown of ring

[Jens Axboe <axboe@kernel.dk>]

On 10/31/22 7:41 AM, Dylan Yudaken wrote:
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index 8d0d40713a63..40b37899e943 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -248,12 +248,20 @@ static unsigned int io_rsrc_retarget_table(struct io_ring_ctx *ctx,
>  	return refs;
>  }
>  
> -static void io_rsrc_retarget_schedule(struct io_ring_ctx *ctx)
> +static void io_rsrc_retarget_schedule(struct io_ring_ctx *ctx, bool delay)
>  	__must_hold(&ctx->uring_lock)
>  {
> -	percpu_ref_get(&ctx->refs);
> -	mod_delayed_work(system_wq, &ctx->rsrc_retarget_work, 60 * HZ);
> -	ctx->rsrc_retarget_scheduled = true;
> +	unsigned long del;
> +
> +	if (delay)
> +		del = 60 * HZ;
> +	else
> +		del = 0;
> +
> +	if (likely(!mod_delayed_work(system_wq, &ctx->rsrc_retarget_work, del))) {
> +		percpu_ref_get(&ctx->refs);
> +		ctx->rsrc_retarget_scheduled = true;
> +	}
>  }

What happens for del == 0 and the work running ala:

CPU 0				CPU 1
mod_delayed_work(.., 0);
				delayed_work runs
					put ctx
percpu_ref_get(ctx)

Also I think that likely() needs to get dropped.

-- 
Jens Axboe