From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793209817; b=nXW5iKmOSw1PYfhbQ0MyEMQOuhW/QpTOkIBQb+9eFv8jWH74Yfdl3Pt9yHSu61av8Vfn AGYlrCa1Tl4WCEIvrOqPIKVHGsekFlrjfv+iiEom1YcKvcNFu6sdZPhRPIK0nnQA5l9dQ wGACJrWYGi7Ks/Qp6MxS5RS3pvnm0PtwElFTvIIJhF9BBsyKpxFNkiTRgZDQoT+F0shi3 qf40iLeYsLAcMEq51n3LfntRb9rWf+zzLTXjKG73dO1XcOv0TwMIo2uqU+/Svx81wLdfL qVzQ0AwWBRSN1fGyfU+f2Ga2WmJssq+h2mJbqqfM66HpAaHdK9jACT/cyPcU7jEihbg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793209817; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=0EQnKxm5FtEmzCVwwMbYiTWTL0aogUYh2EAGkfbcb2E=; b=XfH970KFkG8hwTGyz9lR3MqHtP0NUmZHlgTRa+flVhWMUB3oSn0FZ1iYDj3hXAh/hINw ILOmWUPBKpLuGQ/pgv402GmcMZ25esW3jIJKL42+0Mc8oU9kkVCrlFyyNHmi8pZ3zuPm5 qIantPhpul9zG12KV18A16yxZnQwj8G9MBcIR9cnd40s0+pQU4miA2H6JWGYIrsEM6Ny+ DSaBfXfPKiD1eyIiwSuaO1Pc28Ru0V5UB6ooP1zlaOqpwLaWPjRhkdKkhGRaIAcOq4w9h ZvHiwtrINPLAs+7eRa0kjfvL3BFQBOUa8IiBv/s60D/cbs1Ohe6qBAcPfl7KJ18pJMg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=TnCJo6C6; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1304606A31C; Wed, 28 Oct 2026 17:50:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=TnCJo6C6 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2CBD41F01829; Wed, 28 Oct 2026 17:50:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793209816; bh=0EQnKxm5FtEmzCVwwMbYiTWTL0aogUYh2EAGkfbcb2E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TnCJo6C67eJc7lOSdZWMHO9iwjJunQjwJrV6Z3T53+rwddVXjbLvnztzj+kvvDEAu BzUN0JcQiOW5hxxKRHLRBvj/0wk5Z+Ps8e7jZCdIf91KwJMAtOTAraYRN6wjv3s8+m XHMmozvJXOCK3eCyxbcrLsdRjvYgiKmypNDhTX4M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jens Axboe , "Claude Fable 5.1" Subject: [PATCH 6.18 085/109] io_uring/poll: dont loop on HUP with multiple references Date: Wed, 28 Oct 2026 18:01:09 +0100 Message-ID: <20261028165944.358142059@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165942.357251485@linuxfoundation.org> References: <20261028165942.357251485@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jens Axboe Commit cf1d5c9d335e2c673811da641531da82cb01393a upstream. io_poll_check_events() drops down to one reference when a multishot request sees HUP with more than one, so that the loop goes around once more. It did so by subtracting one less than it had. With the cmpxchg that only takes the local count down: the exchange fails, the next pass reads the unchanged count, and goes through the same motions again. The loop then only ends once io_poll_issue() stops the request. Drop the extra references from the counter instead, and loop once more without trying the exchange. The next pass sees one reference, like it did before, and ends unless a wake up came in. Fixes: 937d38dcacd6 ("io_uring/poll: avoid retry wakeup loss when dropping ownership") Signed-off-by: Jens Axboe Co-Authored-By: Claude Fable 5.1 Signed-off-by: Greg Kroah-Hartman --- io_uring/poll.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -223,12 +223,14 @@ static inline void io_poll_execute(struc */ static int io_poll_check_events(struct io_kiocb *req, io_tw_token_t tw) { + bool again; int v; if (unlikely(tw.cancel)) return -ECANCELED; do { + again = false; v = atomic_read(&req->poll_refs); if (unlikely(v != 1)) { @@ -290,9 +292,15 @@ static int io_poll_check_events(struct i } else { int ret; - /* multiple refs and HUP, ensure we loop once more */ - if ((req->cqe.res & (POLLHUP | POLLRDHUP)) && v != 1) - v--; + /* + * Multiple refs and HUP, ensure we loop once more. Drop + * down to one ref now, so the next pass ends unless a + * wake up came in. + */ + if ((req->cqe.res & (POLLHUP | POLLRDHUP)) && v != 1) { + atomic_sub(v - 1, &req->poll_refs); + again = true; + } ret = io_poll_issue(req, tw); if (ret == IOU_COMPLETE) @@ -311,7 +319,7 @@ static int io_poll_check_events(struct i * task_work while we were executing it. */ v &= IO_POLL_REF_MASK; - } while (atomic_cmpxchg(&req->poll_refs, v, 0) != v); + } while (again || atomic_cmpxchg(&req->poll_refs, v, 0) != v); io_napi_add(req); return IOU_POLL_NO_ACTION;