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=1793209805; b=Ge1NCavtkSu4t0gxr9GZKnEuqWQt8u3YTBp+fC/y/bUxEG+mB2Ppu0GLxOMYK0Q+CIvT GFdNiY9jxLcx8X14l5RSj3pk7iKDxyPqDqHW8RUhn7HV5iZrhM79s6AS2ncbsUSXYlNyM wfFYL+7eo877M6QrtDPgt3q/4j4c8xuJSdAYH5CoJj4/zoSUXj0ys6JI4zSEBYi+lK4C5 9F19io/g942KLbSgWfKxCBuwOwlVyP6bWgadkjdE8DJmB2XumPh48jOvONV8SJgvB1QTI Ls2+iqhjh8YzgXdlwOAB6PQyj9rP+YptPMZ7sIuk0ZMZhWyyCwRbW6M27AndQn5nyOA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793209805; 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=CvIoEbJrJVyuXstc3betopEXa722VPIif7YFvJRj2DY=; b=futXV+CHOoPlB4k8/N2l4bJKE9wL/lTJY6Maf/18egIlweZitwC1Oa0S1Ukozv2ctvP0 kR954ahwEqYGt7MO/cY/wvV09+fW1oYz6H9aJJxJhfTRNrrTU396bV/Selb2ImZkjyv0q mnLh49rb9s/fgS4vtRmTlK6h81YT9mHV0R45IEjm3qqqtFjQ1V4rGLdNHhlZtZNycz6pq EOou3Gy7SGhvA2YAdAY5YgifGRsedQTeFca/E5di/0XnVii4+OmWE2K5aOoN1uCTpYeBO XekZGrZ9KMVwtbHIOnOwvJoPQYICrj4frfvBItQmMWS6F1wykS46rEKZm+T/6DDZ2RQ== 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=M0wtGGM4; 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 4E8D8606A31A; Wed, 28 Oct 2026 17:50:05 +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=M0wtGGM4 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B7F51F01825; Wed, 28 Oct 2026 17:50:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793209805; bh=CvIoEbJrJVyuXstc3betopEXa722VPIif7YFvJRj2DY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=M0wtGGM4Tw45uMB4FWp9P95cQy5hk6ABRF8HnXBlKdFS2uqFNfNlmpHabP3Ezar/B ky7b3ixu59/wM59M9EFjL+GvQBhj+y/LCvjBlXS0WbSEWFDy6M+1l6x93jKsB9kAmY ZW9HlaZUf4SE3KYf34jo45hnHixx94/c1JdQP3bU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Juanlu Herrero , Anand Natarajan , Jens Axboe Subject: [PATCH 6.18 081/109] io_uring/poll: avoid retry wakeup loss when dropping ownership Date: Wed, 28 Oct 2026 18:01:05 +0100 Message-ID: <20261028165944.262826494@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: Juanlu Herrero Commit 937d38dcacd675dc0572d6c9b6743960df3128ed upstream. If a wakeup sets IO_POLL_RETRY_FLAG between the owning task consuming the existing instance of IO_POLL_RETRY_FLAG and the loop check of io_poll_check_events(), then we stall on processing the request until an unrelated wakeup comes along. Using atomic_cmpxchg instead of atomic_sub_return to guarantee both the count v and poll_refs are 0 and no wake-ups are missed. Cc: stable@vger.kernel.org Fixes: a26a35e9019f ("io_uring: make poll refs more robust") Signed-off-by: Juanlu Herrero Assisted-by: LLM Suggested-by: Anand Natarajan Link: https://patch.msgid.link/20261013-pu-cmpxchg-v1-1-4ddc10fd8a03@fastmail.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- io_uring/poll.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -310,7 +310,8 @@ static int io_poll_check_events(struct i * Release all references, retry if someone tried to restart * task_work while we were executing it. */ - } while (atomic_sub_return(v, &req->poll_refs) & IO_POLL_REF_MASK); + v &= IO_POLL_REF_MASK; + } while (atomic_cmpxchg(&req->poll_refs, v, 0) != v); io_napi_add(req); return IOU_POLL_NO_ACTION;