From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 3x6m6g2wPbzDqkJ for ; Wed, 12 Jul 2017 14:23:55 +1000 (AEST) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6C4Nq86046729 for ; Wed, 12 Jul 2017 00:23:52 -0400 Received: from e23smtp03.au.ibm.com (e23smtp03.au.ibm.com [202.81.31.145]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bncj58997-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 12 Jul 2017 00:23:38 -0400 Received: from localhost by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 12 Jul 2017 14:23:35 +1000 Received: from d23av06.au.ibm.com (d23av06.au.ibm.com [9.190.235.151]) by d23relay09.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v6C4NW3i25755718 for ; Wed, 12 Jul 2017 14:23:32 +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 v6C4NVc1007255 for ; Wed, 12 Jul 2017 14:23:31 +1000 From: Cyril Bur To: linuxppc-dev@lists.ozlabs.org, linux-mtd@lists.infradead.org Cc: benh@kernel.crashing.org, stewart@linux.vnet.ibm.com, dwmw2@infradead.org, rlippert@google.com, alistair@popple.id.au Subject: [PATCH v3 07/10] powernv/opal-sensor: remove not needed lock Date: Wed, 12 Jul 2017 14:23:01 +1000 In-Reply-To: <20170712042304.19745-1-cyrilbur@gmail.com> References: <20170712042304.19745-1-cyrilbur@gmail.com> Message-Id: <20170712042304.19745-8-cyrilbur@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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); -- 2.13.2