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Date:   Thu, 15 Aug 2019 11:46:28 -0700
Message-Id: <20190815184628.183186-1-yabinc@google.com>
Mime-Version: 1.0
Subject: [PATCH v3] coresight: tmc-etr: Fix perf_data check.
From:   Yabin Cui <yabinc@google.com>
To:     Mathieu Poirier <mathieu.poirier@linaro.org>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Yabin Cui <yabinc@google.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

When tracing etm data of multiple threads on multiple cpus through
perf interface, each cpu has a unique etr_perf_buffer while sharing
the same etr device. There is no guarantee that the last cpu starts
etm tracing also stops last. This makes perf_data check fail.

Fix it by checking etr_buf instead of etr_perf_buffer.
Also move the code setting and clearing perf_buf to more suitable
places.

Fixes: 3147da92a8a8 ("coresight: tmc-etr: Allocate and free ETR memory buffers for CPU-wide scenarios")
Signed-off-by: Yabin Cui <yabinc@google.com>
---

v2 -> v3:
  moved place of setting drvdata->perf_buf based on review comment.
  Also moved place of clearing drvdata->perf_buf from
  tmc_update_etr_buffer() to tmc_disable_etr_sink() for below
  situation:

  cpu 0 enable etr device (set perf_buf)
  cpu 0 update etr buffer (clear perf_buf)
  cpu 1 enable etr device (perf_buf isn't set because pid set by cpu 0)
  cpu 0 disable etr device
  cpu 1 update etr buffer (perf_buf == NULL, check fails)

  To fix it, we need to move clearing perf_buf to the disable function.

---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 8 ++++----
 drivers/hwtracing/coresight/coresight-tmc.h     | 6 +++---
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 17006705287a..80af313f55d7 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1484,7 +1484,7 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
 		goto out;
 	}
 
-	if (WARN_ON(drvdata->perf_data != etr_perf)) {
+	if (WARN_ON(drvdata->perf_buf != etr_buf)) {
 		lost = true;
 		spin_unlock_irqrestore(&drvdata->spinlock, flags);
 		goto out;
@@ -1496,8 +1496,6 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
 	tmc_sync_etr_buf(drvdata);
 
 	CS_LOCK(drvdata->base);
-	/* Reset perf specific data */
-	drvdata->perf_data = NULL;
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	size = etr_buf->len;
@@ -1556,7 +1554,6 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data)
 	}
 
 	etr_perf->head = PERF_IDX2OFF(handle->head, etr_perf);
-	drvdata->perf_data = etr_perf;
 
 	/*
 	 * No HW configuration is needed if the sink is already in
@@ -1572,6 +1569,7 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data)
 		/* Associate with monitored process. */
 		drvdata->pid = pid;
 		drvdata->mode = CS_MODE_PERF;
+		drvdata->perf_buf = etr_perf->etr_buf;
 		atomic_inc(csdev->refcnt);
 	}
 
@@ -1617,6 +1615,8 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev)
 	/* Dissociate from monitored process. */
 	drvdata->pid = -1;
 	drvdata->mode = CS_MODE_DISABLED;
+	/* Reset perf specific data */
+	drvdata->perf_buf = NULL;
 
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 1ed50411cc3c..f9a0c95e9ba2 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -178,8 +178,8 @@ struct etr_buf {
  *		device configuration register (DEVID)
  * @idr:	Holds etr_bufs allocated for this ETR.
  * @idr_mutex:	Access serialisation for idr.
- * @perf_data:	PERF buffer for ETR.
- * @sysfs_data:	SYSFS buffer for ETR.
+ * @sysfs_buf:	SYSFS buffer for ETR.
+ * @perf_buf:	PERF buffer for ETR.
  */
 struct tmc_drvdata {
 	void __iomem		*base;
@@ -202,7 +202,7 @@ struct tmc_drvdata {
 	struct idr		idr;
 	struct mutex		idr_mutex;
 	struct etr_buf		*sysfs_buf;
-	void			*perf_data;
+	struct etr_buf		*perf_buf;
 };
 
 struct etr_buf_operations {
-- 
2.23.0.rc1.153.gdeed80330f-goog