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 25887350D52; Tue, 26 Aug 2025 13:49:39 +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=1756216179; cv=none; b=VGGNZDzvxqizoHyrFk/ih1ovkR2EhXwO1TAQgodoyk9G4wBVJO0LWB1Tke0cHdFCV8rqgb+zav9tQRcDarKbHgvyDCuaNrtDkIzt+7JPUFJEfoURF9x4dbEhFEGQBVZhOmqnrpZx+pSNOxLg09R0vVndm4qvX+vnUPGub50qh1o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756216179; c=relaxed/simple; bh=nyjnx5EdbYfXuOZkozfU+Fv/EFhHkQBG2a0d7aPu2dM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=c8H3//S8EwROfx9VmKgkqb90012yuLStv7ldfI9T4dPfSjG94Ha+ruOi+F3/4qwXfGCkv81qRfr/4OGtifewn2WKGlklr/1wE56jaO/ZuyNUbv3Kv3HCwHw1F9tmj90xbbVmYyTIXOdBfXfhkfWlWDlQRjY7k7zhwXlKRLpUn2Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=n5PcS9Ay; 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="n5PcS9Ay" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB04CC4CEF1; Tue, 26 Aug 2025 13:49:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756216179; bh=nyjnx5EdbYfXuOZkozfU+Fv/EFhHkQBG2a0d7aPu2dM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=n5PcS9Ayfq4U9NPyWVbtSkAgFIRntd+95UT93sNZAfmXOJXGb9dSy9nqFD4XYJqdI pJIKN3sVIoII50ov3652fi6DH9AyM3BXGLJmjI3oVHiOiredfP8MpaQjJCnr1tQEET B6jr8E3wCSkkA+YWrQYO1bWNdrNsPLn2WknyrVeA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hsin-Te Yuan , "Rafael J. Wysocki" , Sasha Levin Subject: [PATCH 5.15 315/644] thermal: sysfs: Return ENODATA instead of EAGAIN for reads Date: Tue, 26 Aug 2025 13:06:46 +0200 Message-ID: <20250826110954.191246847@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110946.507083938@linuxfoundation.org> References: <20250826110946.507083938@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hsin-Te Yuan [ Upstream commit 1a4aabc27e95674837f2e25f4ef340c0469e6203 ] According to POSIX spec, EAGAIN returned by read with O_NONBLOCK set means the read would block. Hence, the common implementation in nonblocking model will poll the file when the nonblocking read returns EAGAIN. However, when the target file is thermal zone, this mechanism will totally malfunction because thermal zone doesn't implement sysfs notification and thus the poll will never return. For example, the read in Golang implemnts such method and sometimes hangs at reading some thermal zones via sysfs. Change to return -ENODATA instead of -EAGAIN to userspace. Signed-off-by: Hsin-Te Yuan Link: https://patch.msgid.link/20250620-temp-v3-1-6becc6aeb66c@chromium.org Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin --- drivers/thermal/thermal_sysfs.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c index de7cdec3db90..a21af02f6347 100644 --- a/drivers/thermal/thermal_sysfs.c +++ b/drivers/thermal/thermal_sysfs.c @@ -39,10 +39,13 @@ temp_show(struct device *dev, struct device_attribute *attr, char *buf) ret = thermal_zone_get_temp(tz, &temperature); - if (ret) - return ret; + if (!ret) + return sprintf(buf, "%d\n", temperature); - return sprintf(buf, "%d\n", temperature); + if (ret == -EAGAIN) + return -ENODATA; + + return ret; } static ssize_t -- 2.39.5