From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 150B1C433EF for ; Mon, 14 Feb 2022 10:38:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343616AbiBNKiT (ORCPT ); Mon, 14 Feb 2022 05:38:19 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:41894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348358AbiBNKet (ORCPT ); Mon, 14 Feb 2022 05:34:49 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C3936178; Mon, 14 Feb 2022 02:01:55 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D754FB80E0D; Mon, 14 Feb 2022 10:01:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5F86C340F2; Mon, 14 Feb 2022 10:01:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1644832912; bh=CZLhnC2bJWNiM3wvuHY9Uh4DOezRKY5x4zwTTBr13EM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EeFf9k9GrUeEg7NlNCMvkr/XPpFPJnbpQlgK67GLzrALXvmce2zsj54fkAv6eDpYl sNwrbCJfO+FHJY7lkrQJICA4oI375EzfjVF4Tctk/Tq6OYDEt9O+qxAGTmmABRXcST rBmNrhqMmQ2HYPd94B9rhrmuzBVFvnxWvqPFCX5s= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kosuke Tatsukawa Subject: [PATCH 5.16 164/203] n_tty: wake up poll(POLLRDNORM) on receiving data Date: Mon, 14 Feb 2022 10:26:48 +0100 Message-Id: <20220214092515.810641912@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220214092510.221474733@linuxfoundation.org> References: <20220214092510.221474733@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: TATSUKAWA KOSUKE (立川 江介) commit c816b2e65b0e86b95011418cad334f0524fc33b8 upstream. The poll man page says POLLRDNORM is equivalent to POLLIN when used as an event. $ man poll POLLRDNORM Equivalent to POLLIN. However, in n_tty driver, POLLRDNORM does not return until timeout even if there is terminal input, whereas POLLIN returns. The following test program works until kernel-3.17, but the test stops in poll() after commit 57087d515441 ("tty: Fix spurious poll() wakeups"). [Steps to run test program] $ cc -o test-pollrdnorm test-pollrdnorm.c $ ./test-pollrdnorm foo <-- Type in something from the terminal followed by [RET]. The string should be echoed back. ------------------------< test-pollrdnorm.c >------------------------ #include #include #include #include void main(void) { int n; unsigned char buf[8]; struct pollfd fds[1] = {{ 0, POLLRDNORM, 0 }}; n = poll(fds, 1, -1); if (n < 0) perror("poll"); n = read(0, buf, 8); if (n < 0) perror("read"); if (n > 0) write(1, buf, n); } ------------------------------------------------------------------------ The attached patch fixes this problem. Many calls to wake_up_interruptible_poll() in the kernel source code already specify "POLLIN | POLLRDNORM". Fixes: 57087d515441 ("tty: Fix spurious poll() wakeups") Cc: stable@vger.kernel.org Signed-off-by: Kosuke Tatsukawa Link: https://lore.kernel.org/r/TYCPR01MB81901C0F932203D30E452B3EA5209@TYCPR01MB8190.jpnprd01.prod.outlook.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1369,7 +1369,7 @@ handle_newline: put_tty_queue(c, ldata); smp_store_release(&ldata->canon_head, ldata->read_head); kill_fasync(&tty->fasync, SIGIO, POLL_IN); - wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); + wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM); return; } } @@ -1589,7 +1589,7 @@ static void __receive_buf(struct tty_str if (read_cnt(ldata)) { kill_fasync(&tty->fasync, SIGIO, POLL_IN); - wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); + wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM); } }