From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1dUNYD-0000wu-N1 for linux-mtd@lists.infradead.org; Mon, 10 Jul 2017 01:31:51 +0000 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6A1SYuO077357 for ; Sun, 9 Jul 2017 21:31:33 -0400 Received: from e23smtp04.au.ibm.com (e23smtp04.au.ibm.com [202.81.31.146]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bjuj0sjc0-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 09 Jul 2017 21:31:33 -0400 Received: from localhost by e23smtp04.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 10 Jul 2017 11:31:31 +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 v6A1VSYt4456520 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 v6A1VRIC030307 for ; Mon, 10 Jul 2017 11:31:28 +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 v2 07/10] powernv/opal-sensor: remove not needed lock Date: Mon, 10 Jul 2017 11:31:03 +1000 In-Reply-To: <20170710013106.27276-1-cyrilbur@gmail.com> References: <20170710013106.27276-1-cyrilbur@gmail.com> Message-Id: <20170710013106.27276-8-cyrilbur@gmail.com> List-Id: Linux MTD discussion mailing 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