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=1793207326; b=5m3SsCaA6fgKohTIN6J0TIH7Wg/kbEPxTzRjZWBrm0pqvhVfJNeFAlumlLvGpCVoLgy5 0xge5W86gLi8kjS5KrV8iKRNvQUofDib4FDiOAqjC9ZUvXsmX7zo8m4EIpYttvt67pYhO dnT+u1fL4sfuWptVO3wXTUu+6NzMkhelO3NaVJkQoQzXLgK2Z9gYfVMfOOFiaBy5sH07H 6YSy2dNB9VEnpEVw7+IxjGSK2KW1csk/nXq56VG8lHYFyD0vHc1e42Qw9fyHIRg9EDDUC rVh57Kc8eK6ADKOAftoWEainF8vasWNsd2PPoDi1+0mSAOtzGWMZ0GXAprmzHWsPiAg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793207326; 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=b9bKu96HXk9m1koOnJym8uAamtDFRCbZJVB0gQJuNXY=; b=WuoZSeIMSFxr0TXhCoCadXC/iW1OnKAQUi6kGg9DnuuLqjOoFpXBAhBBlN2ITADKBzmo Wd/5hUBa/b41YvL3c+IGbNvSMLTj0zgY3yO5s7AWyyF6nRVrGKm9iBjVjjzIgUlxTKdn7 YZGdEF4Aa+bzoJZHQwpu5rIbbxeCWZ+hp0pcijD1lths0KwIpewS2wkOiwLka5sHa/Hfp hdTHbt/w7WLO7/89BzZFxcllakilFtsrHS3wbshHzuIoFXCl8CAOIV7Zj3GbuGx7kCbzn O4+raBiVTjtqiYJVPuW9Zp+tY3R/eK3ZK0pBIUqwMQCv7e4tpODZtSVw9TVZZscIZxg== 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=fa7yUad8; 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 54B0E606A31A; Wed, 28 Oct 2026 17:08:46 +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=fa7yUad8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id A618E1F01825; Wed, 28 Oct 2026 17:08:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793207326; bh=b9bKu96HXk9m1koOnJym8uAamtDFRCbZJVB0gQJuNXY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=fa7yUad8qe0FPJIKq67crEtkHFZaE4bAdyrT7sgJrIEcmCc/I1YOnV+xlffNVK+ok VLx7bTNDyTanIB3boxA96HdpcopBfx8PVJ66m/63XTOMkx3KGoDI9XtSR37VZw3mUj 5DryhI4AhNZLF8uUOhG2WUbfGvFB3i+rbeYJh6MU= 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 7.2 64/88] io_uring/poll: dont loop on HUP with multiple references Date: Wed, 28 Oct 2026 18:00:12 +0100 Message-ID: <20261028165943.621985543@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165942.107695352@linuxfoundation.org> References: <20261028165942.107695352@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 7.2-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 @@ -241,12 +241,14 @@ 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)) { @@ -310,9 +312,15 @@ 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) @@ -331,7 +339,7 @@ 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;