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Subject[PATCH 18/32] coresight: Move reference counting inside sink drivers
Date
When operating in CPU-wide mode with an N:1 source/sink HW topology,
multiple CPUs can access a sink concurrently. As such reference counting
needs to happen when the device's spinlock is held to avoid racing with
other operations (start(), update(), stop()), such as:

session A Session B
----- -------

enable_sink
atomic_inc(refcount) = 1

...

atomic_dec(refcount) = 0 enable_sink
if (refcount == 0) disable_sink
atomic_inc()

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Robert Walker <robert.walker@arm.com>
---
drivers/hwtracing/coresight/coresight-etb10.c | 21 ++++++++++----
.../hwtracing/coresight/coresight-tmc-etf.c | 21 +++++++++++---
.../hwtracing/coresight/coresight-tmc-etr.c | 19 +++++++++++--
drivers/hwtracing/coresight/coresight-tpiu.c | 6 +++-
drivers/hwtracing/coresight/coresight.c | 28 +++++++++----------
5 files changed, 66 insertions(+), 29 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 23b049cef19a..8e63863cf950 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -5,6 +5,7 @@
* Description: CoreSight Embedded Trace Buffer driver
*/

+#include <linux/atomic.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/types.h>
@@ -151,14 +152,15 @@ static int etb_enable_sysfs(struct coresight_device *csdev)
goto out;
}

- /* Nothing to do, the tracer is already enabled. */
- if (drvdata->mode == CS_MODE_SYSFS)
- goto out;
+ if (drvdata->mode == CS_MODE_DISABLED) {
+ ret = etb_enable_hw(drvdata);
+ if (ret)
+ goto out;

- ret = etb_enable_hw(drvdata);
- if (!ret)
drvdata->mode = CS_MODE_SYSFS;
+ }

+ atomic_inc(csdev->refcnt);
out:
spin_unlock_irqrestore(&drvdata->spinlock, flags);
return ret;
@@ -188,8 +190,10 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data)
goto out;

ret = etb_enable_hw(drvdata);
- if (!ret)
+ if (!ret) {
drvdata->mode = CS_MODE_PERF;
+ atomic_inc(csdev->refcnt);
+ }

out:
spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -324,6 +328,11 @@ static int etb_disable(struct coresight_device *csdev)

spin_lock_irqsave(&drvdata->spinlock, flags);

+ if (atomic_dec_return(csdev->refcnt)) {
+ spin_unlock_irqrestore(&drvdata->spinlock, flags);
+ return -EBUSY;
+ }
+
/* Disable the ETB only if it needs to */
if (drvdata->mode != CS_MODE_DISABLED) {
etb_disable_hw(drvdata);
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index d4213e7c2c45..d50a608a60f1 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -4,6 +4,7 @@
* Author: Mathieu Poirier <mathieu.poirier@linaro.org>
*/

+#include <linux/atomic.h>
#include <linux/circ_buf.h>
#include <linux/coresight.h>
#include <linux/perf_event.h>
@@ -180,8 +181,10 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
* sink is already enabled no memory is needed and the HW need not be
* touched.
*/
- if (drvdata->mode == CS_MODE_SYSFS)
+ if (drvdata->mode == CS_MODE_SYSFS) {
+ atomic_inc(csdev->refcnt);
goto out;
+ }

/*
* If drvdata::buf isn't NULL, memory was allocated for a previous
@@ -200,11 +203,13 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
}

ret = tmc_etb_enable_hw(drvdata);
- if (!ret)
+ if (!ret) {
drvdata->mode = CS_MODE_SYSFS;
- else
+ atomic_inc(csdev->refcnt);
+ } else {
/* Free up the buffer if we failed to enable */
used = false;
+ }
out:
spin_unlock_irqrestore(&drvdata->spinlock, flags);

@@ -239,8 +244,10 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data)
if (ret)
break;
ret = tmc_etb_enable_hw(drvdata);
- if (!ret)
+ if (!ret) {
drvdata->mode = CS_MODE_PERF;
+ atomic_inc(csdev->refcnt);
+ }
} while (0);
spin_unlock_irqrestore(&drvdata->spinlock, flags);

@@ -279,11 +286,17 @@ static int tmc_disable_etf_sink(struct coresight_device *csdev)
struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

spin_lock_irqsave(&drvdata->spinlock, flags);
+
if (drvdata->reading) {
spin_unlock_irqrestore(&drvdata->spinlock, flags);
return -EBUSY;
}

+ if (atomic_dec_return(csdev->refcnt)) {
+ spin_unlock_irqrestore(&drvdata->spinlock, flags);
+ return -EBUSY;
+ }
+
/* Disable the TMC only if it needs to */
if (drvdata->mode != CS_MODE_DISABLED) {
tmc_etb_disable_hw(drvdata);
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index c6a0f5897684..6a8f39d03de3 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -4,6 +4,7 @@
* Author: Mathieu Poirier <mathieu.poirier@linaro.org>
*/

+#include <linux/atomic.h>
#include <linux/coresight.h>
#include <linux/dma-mapping.h>
#include <linux/iommu.h>
@@ -1125,8 +1126,10 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev)
* sink is already enabled no memory is needed and the HW need not be
* touched, even if the buffer size has changed.
*/
- if (drvdata->mode == CS_MODE_SYSFS)
+ if (drvdata->mode == CS_MODE_SYSFS) {
+ atomic_inc(csdev->refcnt);
goto out;
+ }

/*
* If we don't have a buffer or it doesn't match the requested size,
@@ -1139,8 +1142,10 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev)
}

ret = tmc_etr_enable_hw(drvdata, drvdata->sysfs_buf);
- if (!ret)
+ if (!ret) {
drvdata->mode = CS_MODE_SYSFS;
+ atomic_inc(csdev->refcnt);
+ }
out:
spin_unlock_irqrestore(&drvdata->spinlock, flags);

@@ -1371,8 +1376,10 @@ 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;
rc = tmc_etr_enable_hw(drvdata, etr_perf->etr_buf);
- if (!rc)
+ if (!rc) {
drvdata->mode = CS_MODE_PERF;
+ atomic_inc(csdev->refcnt);
+ }

unlock_out:
spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -1399,11 +1406,17 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev)
struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

spin_lock_irqsave(&drvdata->spinlock, flags);
+
if (drvdata->reading) {
spin_unlock_irqrestore(&drvdata->spinlock, flags);
return -EBUSY;
}

+ if (atomic_dec_return(csdev->refcnt)) {
+ spin_unlock_irqrestore(&drvdata->spinlock, flags);
+ return -EBUSY;
+ }
+
/* Disable the TMC only if it needs to */
if (drvdata->mode != CS_MODE_DISABLED) {
tmc_etr_disable_hw(drvdata);
diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c b/drivers/hwtracing/coresight/coresight-tpiu.c
index c1b77e3c3187..63d9af31f57f 100644
--- a/drivers/hwtracing/coresight/coresight-tpiu.c
+++ b/drivers/hwtracing/coresight/coresight-tpiu.c
@@ -5,6 +5,7 @@
* Description: CoreSight Trace Port Interface Unit driver
*/

+#include <linux/atomic.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/device.h>
@@ -73,7 +74,7 @@ static int tpiu_enable(struct coresight_device *csdev, u32 mode, void *__unused)
struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

tpiu_enable_hw(drvdata);
-
+ atomic_inc(csdev->refcnt);
dev_dbg(drvdata->dev, "TPIU enabled\n");
return 0;
}
@@ -98,6 +99,9 @@ static int tpiu_disable(struct coresight_device *csdev)
{
struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

+ if (atomic_dec_return(csdev->refcnt))
+ return -EBUSY;
+
tpiu_disable_hw(drvdata);

dev_dbg(drvdata->dev, "TPIU disabled\n");
diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 66c25b0a785e..4b130281236a 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -225,14 +225,13 @@ static int coresight_enable_sink(struct coresight_device *csdev,
* We need to make sure the "new" session is compatible with the
* existing "mode" of operation.
*/
- if (sink_ops(csdev)->enable) {
- ret = sink_ops(csdev)->enable(csdev, mode, data);
- if (ret)
- return ret;
- csdev->enable = true;
- }
+ if (!sink_ops(csdev)->enable)
+ return -EINVAL;

- atomic_inc(csdev->refcnt);
+ ret = sink_ops(csdev)->enable(csdev, mode, data);
+ if (ret)
+ return ret;
+ csdev->enable = true;

return 0;
}
@@ -241,14 +240,13 @@ static void coresight_disable_sink(struct coresight_device *csdev)
{
int ret;

- if (atomic_dec_return(csdev->refcnt) == 0) {
- if (sink_ops(csdev)->disable) {
- ret = sink_ops(csdev)->disable(csdev);
- if (ret)
- return;
- csdev->enable = false;
- }
- }
+ if (!sink_ops(csdev)->disable)
+ return;
+
+ ret = sink_ops(csdev)->disable(csdev);
+ if (ret)
+ return;
+ csdev->enable = false;
}

static int coresight_enable_link(struct coresight_device *csdev,
--
2.17.1
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