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Sat, 25 Oct 2025 21:10:41 -0700 (PDT) Message-ID: <74ce4fb9-3654-4a1d-9b8b-abee8aba9ca9@davidwei.uk> Date: Sat, 25 Oct 2025 21:10:41 -0700 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] io_uring/zcrx: add refcount to struct io_zcrx_ifq To: Jens Axboe , io-uring@vger.kernel.org, netdev@vger.kernel.org Cc: Pavel Begunkov References: <20251025191504.3024224-1-dw@davidwei.uk> <20251025191504.3024224-3-dw@davidwei.uk> <0a9d9e34-a351-4168-bbdc-3ca3b6c3e17b@kernel.dk> Content-Language: en-US From: David Wei In-Reply-To: <0a9d9e34-a351-4168-bbdc-3ca3b6c3e17b@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025-10-25 16:37, Jens Axboe wrote: > On 10/25/25 1:15 PM, David Wei wrote: >> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c >> index a816f5902091..22d759307c16 100644 >> --- a/io_uring/zcrx.c >> +++ b/io_uring/zcrx.c >> @@ -730,6 +731,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx) >> lockdep_assert_held(&ctx->uring_lock); >> >> xa_for_each(&ctx->zcrx_ctxs, index, ifq) { >> + if (refcount_read(&ifq->refs) > 1) >> + continue; > > This is a bit odd, it's not an idiomatic way to use reference counts. > Why isn't this a refcount_dec_and_test()? Given that both the later grab > when sharing is enabled and the shutdown here are under the ->uring_lock > this may not matter, but it'd be a lot more obviously correct if it > looked ala: > > if (refcount_dec_and_test(&ifq->refs)) { > io_zcrx_scrub(ifq); > io_close_queue(ifq); > } > > instead? > Yeah, good idea. Your comments prompted me to try to find a better solution that gets rid of ifq->proxy. Turns out xarray has 3 bits per entry that can be 'marked'. With this I can get a cleaner solution. Will respin tomorrow.