From patchwork Mon Jul 10 01:31:03 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cyril Bur X-Patchwork-Id: 785990 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [103.22.144.68]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3x5SWJ1fMZz9s0Z for ; Mon, 10 Jul 2017 11:37:16 +1000 (AEST) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3x5SWJ0v82zDrHp for ; Mon, 10 Jul 2017 11:37:16 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3x5SNm3bWyzDq7c for ; Mon, 10 Jul 2017 11:31:36 +1000 (AEST) Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6A1SYku103838 for ; Sun, 9 Jul 2017 21:31:34 -0400 Received: from e23smtp01.au.ibm.com (e23smtp01.au.ibm.com [202.81.31.143]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bjucuhc7s-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 09 Jul 2017 21:31:34 -0400 Received: from localhost by e23smtp01.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Mon, 10 Jul 2017 11:31:29 +1000 Received: from d23av06.au.ibm.com (d23av06.au.ibm.com [9.190.235.151]) by d23relay08.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v6A1VSVT15728746 for ; Mon, 10 Jul 2017 11:31:28 +1000 Received: from d23av06.au.ibm.com (localhost [127.0.0.1]) by d23av06.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v6A1VRIE030307 for ; Mon, 10 Jul 2017 11:31:28 +1000 Received: from ozlabs.au.ibm.com (ozlabs.au.ibm.com [9.192.253.14]) by d23av06.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id v6A1VR0L030304; Mon, 10 Jul 2017 11:31:27 +1000 Received: from camb691.ozlabs.ibm.com (haven.au.ibm.com [9.192.254.114]) (using TLSv1.2 with cipher DHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ozlabs.au.ibm.com (Postfix) with ESMTPSA id 56429A0385; Mon, 10 Jul 2017 11:31:27 +1000 (AEST) From: Cyril Bur To: linuxppc-dev@lists.ozlabs.org, linux-mtd@lists.infradead.org Subject: [PATCH v2 07/10] powernv/opal-sensor: remove not needed lock Date: Mon, 10 Jul 2017 11:31:03 +1000 X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170710013106.27276-1-cyrilbur@gmail.com> References: <20170710013106.27276-1-cyrilbur@gmail.com> X-TM-AS-MML: disable x-cbid: 17071001-1617-0000-0000-000001F41303 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17071001-1618-0000-0000-0000483BAF7B Message-Id: <20170710013106.27276-8-cyrilbur@gmail.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-07-09_14:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1707100024 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: stewart@linux.vnet.ibm.com, alistair@popple.id.au, dwmw2@infradead.org, rlippert@google.com Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Stewart Smith Parallel sensor reads could run out of async tokens due to opal_get_sensor_data grabbing tokens but then doing the sensor read behind a mutex, essentially serializing the (possibly asynchronous and relatively slow) sensor read. It turns out that the mutex isn't needed at all, not only should the OPAL interface allow concurrent reads, the implementation is certainly safe for that, and if any sensor we were reading from somewhere isn't, doing the mutual exclusion in the kernel is the wrong place to do it, OPAL should be doing it for the kernel. So, remove the mutex. Additionally, we shouldn't be printing out an error when we don't get a token as the only way this should happen is if we've been interrupted in down_interruptible() on the semaphore. Reported-by: Robert Lippert Signed-off-by: Stewart Smith Signed-off-by: Cyril Bur --- arch/powerpc/platforms/powernv/opal-sensor.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) diff --git a/arch/powerpc/platforms/powernv/opal-sensor.c b/arch/powerpc/platforms/powernv/opal-sensor.c index aa267f120033..0a7074bb91dc 100644 --- a/arch/powerpc/platforms/powernv/opal-sensor.c +++ b/arch/powerpc/platforms/powernv/opal-sensor.c @@ -19,13 +19,10 @@ */ #include -#include #include #include #include -static DEFINE_MUTEX(opal_sensor_mutex); - /* * This will return sensor information to driver based on the requested sensor * handle. A handle is an opaque id for the powernv, read by the driver from the @@ -38,13 +35,9 @@ int opal_get_sensor_data(u32 sensor_hndl, u32 *sensor_data) __be32 data; token = opal_async_get_token_interruptible(); - if (token < 0) { - pr_err("%s: Couldn't get the token, returning\n", __func__); - ret = token; - goto out; - } + if (token < 0) + return token; - mutex_lock(&opal_sensor_mutex); ret = opal_sensor_read(sensor_hndl, token, &data); switch (ret) { case OPAL_ASYNC_COMPLETION: @@ -52,7 +45,7 @@ int opal_get_sensor_data(u32 sensor_hndl, u32 *sensor_data) if (ret) { pr_err("%s: Failed to wait for the async response, %d\n", __func__, ret); - goto out_token; + goto out; } ret = opal_error_code(opal_get_async_rc(msg)); @@ -73,10 +66,8 @@ int opal_get_sensor_data(u32 sensor_hndl, u32 *sensor_data) break; } -out_token: - mutex_unlock(&opal_sensor_mutex); - opal_async_release_token(token); out: + opal_async_release_token(token); return ret; } EXPORT_SYMBOL_GPL(opal_get_sensor_data);