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=1793212150; b=LX5HGzJ+LlDKZnSjuoMy2jGH7Q1dTRVbnOUsROr3IEHO5aScsp8JgeJMNV6vApyqQX2X k9Oew50qLB7WM9X2PhjNTWp/j8ld2bw2BK/LgNCYpxS1JNTJP8kjooQ3/2a4VAYJ85bxr CCxN+0t/EGZYdoMc1B2slcoSeQ+2Kvbh7h7g7eyauHzCa9yvcH42bZFkd3zIpTxdFZ9Mv TJg/z/2B5Ib8mCrbmtVJ3eYunrUj32Bx7yFeELMtMsXMwReZeeqepc53b8GL240t6EsSc jrsU7m75syEdm/NYw2T9sORNrhIJXF5VtzXMBrus2YYXEZhdpmaXiImgDX5XeR3s2uA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793212150; 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=8mh6V8N04NxKH1CMT68qmc9yy2lsiLWtvYYYaKgilaM=; b=HJNss/EucObLLjEHSxBASQ+zs0VRktkiIDaMK2Dqpgf45Vb9vedsAeUlR4jaWuy920VG RPV4eqS9pVVq/bq+tZJbeBk1/3JS+oeCelh3R6kVNDmv/KCIovyn0PvPdPHYiPRbtvrLl bls6ph60iKCzEv8G0mbGtWAbwPU+nQLQzrCr8dKoxhHKR8jJAZlSw0GVVgOj/I0oOvqIG lY4tE2eWyP5Eo7va4jJT2UZpFebl3rKpqsCLVJleebLXJaShVhYJdy5Wf3tgUhwi6asM3 BWR7U4kCe/RURrHFRk4T1sqaz6if0WWYHK16ycpW6soh+d5PcpIzktu2ZHqJHY2lbtw== 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=GMamV8n1; 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 A5B1F606A31C; Wed, 28 Oct 2026 18:29:09 +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=GMamV8n1 Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0B121F01825; Wed, 28 Oct 2026 18:29:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793212149; bh=8mh6V8N04NxKH1CMT68qmc9yy2lsiLWtvYYYaKgilaM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=GMamV8n17xpBN3mPs0LOuImo+BwW/KADhSDZ4ySVZy6SvXj8cc/I4ds4ILgg8u1vY n7eeHCv93AwqaCk3yk3lb41IHzaxXAnCWUnkf8IniJGPAGkRsp8MU4Bd+88vSUGZB0 RBveAtx5vtz6pIpF53M5hGiDs/y99Hq0zKPXV2vo= 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 6.1 0018/1887] io_uring/poll: avoid retry wakeup loss when dropping ownership Date: Wed, 28 Oct 2026 17:35:14 +0100 Message-ID: <20261028170459.636886941@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@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 6.1-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 | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -325,8 +325,8 @@ 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 & IO_POLL_REF_MASK, &req->poll_refs) & - IO_POLL_REF_MASK); + v &= IO_POLL_REF_MASK; + } while (atomic_cmpxchg(&req->poll_refs, v, 0) != v); return IOU_POLL_NO_ACTION; }