linux-kernel - [PATCH v1 1/4] coresight: etm4x: Add lock for reading virtual context ID comparator

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Message-Id: <20211031144214.237879-2-leo.yan@linaro.org>
Date:   Sun, 31 Oct 2021 22:42:11 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        James Clark <james.clark@....com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v1 1/4] coresight: etm4x: Add lock for reading virtual context ID comparator

When read the virtual context ID comparator value via sysfs node, the
driver firstly reads out the index, then reads the comparator value
based on index.

This patch adds the spinlock to protect the atomicity for up two steps.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
index a0640fa5c55b..e4c8c44d04ef 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
@@ -2111,7 +2111,9 @@ static ssize_t vmid_val_show(struct device *dev,
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
 	struct etmv4_config *config = &drvdata->config;
 
+	spin_lock(&drvdata->spinlock);
 	val = (unsigned long)config->vmid_val[config->vmid_idx];
+	spin_unlock(&drvdata->spinlock);
 	return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
 }
 
-- 
2.25.1