From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E63D350D5F; Tue, 26 Aug 2025 14:30:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756218644; cv=none; b=dVHBtDH89ac06+R3l80MFlJqteXqbdYlpPlCXQLzXXHm58hWx0yR8GhbH3LCAe1enyltrjSL5AA+VEN9j6X9kbqUoPu4/Q3tb2HN0NY5gTNDmghGSYd8ILjAPmWo6FpKn7Wv1fpX+h4FvWI7O34kXWod04xber3U8hyfNYyZZe8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756218644; c=relaxed/simple; bh=+O7cxkulEW2wE35tfN2CaAUrIyG5R2JlvGgK4qSVzbQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FaYQbY3ccsYnRq+joJAetFjjs7YN+YTHXf1MPYXw2vAzwV83zfvjHStivTMSNWWab3Hl0eCW/IAGzJhyWS+a+wDVRPPon4C/yXUfFOeTdKdBl6qHU6/XUGnq1ztg4zNbAejVvOkfbIxAcTTSXV8FU8zwwZB3HVHV+0N2sr0vHbw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sY5GGFKN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="sY5GGFKN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61BB6C113D0; Tue, 26 Aug 2025 14:30:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756218643; bh=+O7cxkulEW2wE35tfN2CaAUrIyG5R2JlvGgK4qSVzbQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sY5GGFKNmuhmh1/TnFBwv7wbu6dpnCEiWtffEOSLI/AqssAtYVtUVnXTaOgSsX3fE FIkx4Yhgnu2R/ZRyQiUKqSwbe4QzzhiycOMunaNvt0EBHnlUsecZysNH6SZUqvFHoD wI5b2ThgwsK1rqK5h7jchunncA/SN6c2cqoJJUXM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Denis OSTERLAND-HEIM , Rodolfo Giometti , Sasha Levin Subject: [PATCH 5.4 077/403] pps: fix poll support Date: Tue, 26 Aug 2025 13:06:43 +0200 Message-ID: <20250826110908.548599723@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110905.607690791@linuxfoundation.org> References: <20250826110905.607690791@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Denis OSTERLAND-HEIM [ Upstream commit 12c409aa1ec2592280a2ddcc66ff8f3c7f7bb171 ] Because pps_cdev_poll() returns unconditionally EPOLLIN, a user space program that calls select/poll get always an immediate data ready-to-read response. As a result the intended use to wait until next data becomes ready does not work. User space snippet: struct pollfd pollfd = { .fd = open("/dev/pps0", O_RDONLY), .events = POLLIN|POLLERR, .revents = 0 }; while(1) { poll(&pollfd, 1, 2000/*ms*/); // returns immediate, but should wait if(revents & EPOLLIN) { // always true struct pps_fdata fdata; memset(&fdata, 0, sizeof(memdata)); ioctl(PPS_FETCH, &fdata); // currently fetches data at max speed } } Lets remember the last fetch event counter and compare this value in pps_cdev_poll() with most recent event counter and return 0 if they are equal. Signed-off-by: Denis OSTERLAND-HEIM Co-developed-by: Rodolfo Giometti Signed-off-by: Rodolfo Giometti Fixes: eae9d2ba0cfc ("LinuxPPS: core support") Link: https://lore.kernel.org/all/f6bed779-6d59-4f0f-8a59-b6312bd83b4e@enneenne.com/ Acked-by: Rodolfo Giometti Link: https://lore.kernel.org/r/c3c50ad1eb19ef553eca8a57c17f4c006413ab70.camel@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/pps/pps.c | 11 +++++++++-- include/linux/pps_kernel.h | 1 + 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c index 2d008e0d116a..ea966fc67d28 100644 --- a/drivers/pps/pps.c +++ b/drivers/pps/pps.c @@ -41,6 +41,9 @@ static __poll_t pps_cdev_poll(struct file *file, poll_table *wait) poll_wait(file, &pps->queue, wait); + if (pps->last_fetched_ev == pps->last_ev) + return 0; + return EPOLLIN | EPOLLRDNORM; } @@ -186,9 +189,11 @@ static long pps_cdev_ioctl(struct file *file, if (err) return err; - /* Return the fetched timestamp */ + /* Return the fetched timestamp and save last fetched event */ spin_lock_irq(&pps->lock); + pps->last_fetched_ev = pps->last_ev; + fdata.info.assert_sequence = pps->assert_sequence; fdata.info.clear_sequence = pps->clear_sequence; fdata.info.assert_tu = pps->assert_tu; @@ -272,9 +277,11 @@ static long pps_cdev_compat_ioctl(struct file *file, if (err) return err; - /* Return the fetched timestamp */ + /* Return the fetched timestamp and save last fetched event */ spin_lock_irq(&pps->lock); + pps->last_fetched_ev = pps->last_ev; + compat.info.assert_sequence = pps->assert_sequence; compat.info.clear_sequence = pps->clear_sequence; compat.info.current_mode = pps->current_mode; diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h index c7abce28ed29..aab0aebb529e 100644 --- a/include/linux/pps_kernel.h +++ b/include/linux/pps_kernel.h @@ -52,6 +52,7 @@ struct pps_device { int current_mode; /* PPS mode at event time */ unsigned int last_ev; /* last PPS event id */ + unsigned int last_fetched_ev; /* last fetched PPS event id */ wait_queue_head_t queue; /* PPS event queue */ unsigned int id; /* PPS source unique ID */ -- 2.39.5