diff options
author | Mathieu Poirier <mathieu.poirier@linaro.org> | 2019-04-25 13:52:56 -0600 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-25 22:00:16 +0200 |
commit | f973d88b75703719d39c4d5145079199aaf442b2 (patch) | |
tree | 3abbbcce4aa7204d7584b3bcfaca818f910d7a63 /drivers/hwtracing/coresight/coresight-tmc-etr.c | |
parent | coresight: Adding return code to sink::disable() operation (diff) | |
download | linux-dev-f973d88b75703719d39c4d5145079199aaf442b2.tar.xz linux-dev-f973d88b75703719d39c4d5145079199aaf442b2.zip |
coresight: Move reference counting inside sink drivers
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hwtracing/coresight/coresight-tmc-etr.c')
-rw-r--r-- | drivers/hwtracing/coresight/coresight-tmc-etr.c | 19 |
1 files changed, 16 insertions, 3 deletions
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); |