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authorMathieu Poirier <mathieu.poirier@linaro.org>2016-05-03 11:33:53 -0600
committerMathieu Poirier <mathieu.poirier@linaro.org>2016-06-01 15:46:37 -0600
commit09c5cf1702bf498bd5d30e94eda0d855dbb301df (patch)
tree60258ee4299a188b684e2bac9da59a3c5fc65403
parent17c61c32ab5a2e0ff67e00e4d562ba0a97b999f2 (diff)
coresight: tmc: getting rid of multiple read access
Allowing multiple readers to access the trace data simultaniously via sysFS provides no shortage of opportunity for race condition, mandates two variable to be maintained (drvdata::read_count and drvdata::reading), makes the code complex and provide little advantages, if any. This patch streamlines the read process by restricting trace data access to a single user. That way drvdata::read_count can be eliminated and race conditions (along with faulty error handling) in function tmc_open() and tmc_release() eliminated. Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> (cherry picked from commit f74debbea0885ebb65fb3fa4e598323f40b03f5f)
-rw-r--r--drivers/hwtracing/coresight/coresight-tmc-etf.c5
-rw-r--r--drivers/hwtracing/coresight/coresight-tmc-etr.c4
-rw-r--r--drivers/hwtracing/coresight/coresight-tmc.c24
-rw-r--r--drivers/hwtracing/coresight/coresight-tmc.h2
4 files changed, 18 insertions, 17 deletions
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index 6eb1665cfc9c..60edf4d1968f 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -260,6 +260,11 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
spin_lock_irqsave(&drvdata->spinlock, flags);
+ if (drvdata->reading) {
+ ret = -EBUSY;
+ goto out;
+ }
+
/* There is no point in reading a TMC in HW FIFO mode */
mode = readl_relaxed(drvdata->base + TMC_MODE);
if (mode != TMC_MODE_CIRCULAR_BUFFER) {
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index ac37bf904fb7..d6999b457fb8 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -188,6 +188,10 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
return -EINVAL;
spin_lock_irqsave(&drvdata->spinlock, flags);
+ if (drvdata->reading) {
+ ret = -EBUSY;
+ goto out;
+ }
/* If drvdata::buf is NULL the trace data has been read already */
if (drvdata->buf == NULL) {
diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
index e8e12a9b917a..ae7525a2b94a 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -95,7 +95,7 @@ static int tmc_read_prepare(struct tmc_drvdata *drvdata)
return ret;
}
-static void tmc_read_unprepare(struct tmc_drvdata *drvdata)
+static int tmc_read_unprepare(struct tmc_drvdata *drvdata)
{
int ret = 0;
@@ -113,21 +113,20 @@ static void tmc_read_unprepare(struct tmc_drvdata *drvdata)
if (!ret)
dev_info(drvdata->dev, "TMC read end\n");
+
+ return ret;
}
static int tmc_open(struct inode *inode, struct file *file)
{
+ int ret;
struct tmc_drvdata *drvdata = container_of(file->private_data,
struct tmc_drvdata, miscdev);
- int ret = 0;
-
- if (drvdata->read_count++)
- goto out;
ret = tmc_read_prepare(drvdata);
if (ret)
return ret;
-out:
+
nonseekable_open(inode, file);
dev_dbg(drvdata->dev, "%s: successfully opened\n", __func__);
@@ -167,19 +166,14 @@ static ssize_t tmc_read(struct file *file, char __user *data, size_t len,
static int tmc_release(struct inode *inode, struct file *file)
{
+ int ret;
struct tmc_drvdata *drvdata = container_of(file->private_data,
struct tmc_drvdata, miscdev);
- if (--drvdata->read_count) {
- if (drvdata->read_count < 0) {
- dev_err(drvdata->dev, "mismatched close\n");
- drvdata->read_count = 0;
- }
- goto out;
- }
+ ret = tmc_read_unprepare(drvdata);
+ if (ret)
+ return ret;
- tmc_read_unprepare(drvdata);
-out:
dev_dbg(drvdata->dev, "%s: released\n", __func__);
return 0;
}
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index df661903f83c..592eb149fe3a 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -94,7 +94,6 @@ enum tmc_mem_intf_width {
* @csdev: component vitals needed by the framework.
* @miscdev: specifics to handle "/dev/xyz.tmc" entry.
* @spinlock: only one at a time pls.
- * @read_count: manages preparation of buffer for reading.
* @buf: area of memory where trace data get sent.
* @paddr: DMA start location in RAM.
* @vaddr: virtual representation of @paddr.
@@ -109,7 +108,6 @@ struct tmc_drvdata {
struct coresight_device *csdev;
struct miscdevice miscdev;
spinlock_t spinlock;
- int read_count;
bool reading;
char *buf;
dma_addr_t paddr;