[PATCH v3 6/8] coresight: tmc-etf: Prevent per-thread events from sharing a sink

[James Clark]

Like the previous commit to ETR, ETF sinks shouldn't share per-thread
events. Fix it by returning -EBUSY if a second per-thread event tries to
use the same sink.

Fixes: 880af782c6e8 ("coresight: tmc-etf: Add support for CPU-wide trace scenarios")
Signed-off-by: James Clark <james.clark at linaro.org>
---
 drivers/hwtracing/coresight/coresight-tmc-core.c |  2 --
 drivers/hwtracing/coresight/coresight-tmc-etf.c  | 23 +++++++----------------
 drivers/hwtracing/coresight/coresight-tmc.h      |  4 ----
 3 files changed, 7 insertions(+), 22 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
index 873868718b14..2c2f2f312e8e 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
@@ -800,8 +800,6 @@ static int __tmc_probe(struct device *dev, struct resource *res)
 	devid = readl_relaxed(drvdata->base + CORESIGHT_DEVID);
 	drvdata->config_type = BMVAL(devid, 6, 7);
 	drvdata->memwidth = tmc_get_memwidth(devid);
-	/* This device is not associated with a session */
-	drvdata->pid = -1;
 	drvdata->etr_mode = ETR_MODE_AUTO;
 
 	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index d90090b846ab..c451f1da3cdd 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -250,11 +250,10 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev,
 				    struct coresight_path *path)
 {
 	int ret = 0;
-	pid_t pid;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct perf_output_handle *handle = path->handle;
-	struct cs_buffers *buf = etm_perf_sink_config(handle);
+	struct etm_event_data *event_data = perf_get_aux(handle);
 
 	raw_spin_lock_irqsave(&drvdata->spinlock, flags);
 	do {
@@ -270,10 +269,8 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev,
 			break;
 		}
 
-		/* Get a handle on the pid of the process to monitor */
-		pid = buf->pid;
-
-		if (drvdata->pid != -1 && drvdata->pid != pid) {
+		if (!etm_perf_sink_can_share(csdev, &drvdata->perf_session,
+					     handle)) {
 			ret = -EBUSY;
 			break;
 		}
@@ -282,19 +279,15 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev,
 		if (ret)
 			break;
 
-		/*
-		 * No HW configuration is needed if the sink is already in
-		 * use for this session.
-		 */
-		if (drvdata->pid == pid) {
+		/*  No HW configuration is needed if the sink is already in use. */
+		if (csdev->refcnt) {
 			csdev->refcnt++;
 			break;
 		}
 
 		ret  = tmc_etb_enable_hw(drvdata);
 		if (!ret) {
-			/* Associate with monitored process. */
-			drvdata->pid = pid;
+			drvdata->perf_session = event_data->session_id;
 			coresight_set_mode(csdev, CS_MODE_PERF);
 			csdev->refcnt++;
 		}
@@ -351,9 +344,8 @@ static int tmc_disable_etf_sink(struct coresight_device *csdev)
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(coresight_get_mode(csdev) == CS_MODE_DISABLED);
 	tmc_etb_disable_hw(drvdata);
-	/* Dissociate from monitored process. */
-	drvdata->pid = -1;
 	coresight_set_mode(csdev, CS_MODE_DISABLED);
+	drvdata->perf_session = (struct etm_session_id) {};
 
 	raw_spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -433,7 +425,6 @@ static void *tmc_alloc_etf_buffer(struct coresight_device *csdev,
 	if (!buf)
 		return NULL;
 
-	buf->pid = task_pid_nr(event->owner);
 	buf->snapshot = overwrite;
 	buf->nr_pages = nr_pages;
 	buf->data_pages = pages;
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 0125f2ad78ed..99601ac9179d 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -223,9 +223,6 @@ struct tmc_resrv_buf {
  * @crashdev:	specifics to handle "/dev/crash_tmc_xyz" entry for reading
  *		crash tracedata.
  * @spinlock:	only one at a time pls.
- * @pid:	Process ID of the process that owns the session that is using
- *		this component. For example this would be the pid of the Perf
- *		process.
  * @sysfs_reading: Sysfs mode buffer is being read through "/dev/xyz.tmc" entry.
  *                Note: ETR has a separate software buffer for the two modes so
  *		  the device can still be read while in Perf mode if there is a
@@ -264,7 +261,6 @@ struct tmc_drvdata {
 	struct miscdevice	miscdev;
 	struct miscdevice	crashdev;
 	raw_spinlock_t		spinlock;
-	pid_t			pid;
 	bool			sysfs_reading;
 	bool			stop_on_flush;
 	union {

-- 
2.34.1