[PATCH v4 9/9] coresight: etm3x: remove redundant call etm_enable_hw() with hotplug

[Yeoreum Yun]

The cpu_online_mask is set at the CPUHP_BRINGUP_CPU step.
In other words, if etm4_enable_sysfs() is called between
CPUHP_BRINGUP_CPU and CPUHP_AP_ARM_CORESIGHT_STARTING,
etm_enable_hw() may be invoked in etm_enable_sysfs_smp_call()
and then executed again in etm_starting_cpu().

To remove this redundant call, take the hotplug lock before executing
etm_enable_sysfs_smp_call().

Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>
---
 .../coresight/coresight-etm3x-core.c          | 24 +++++++++----------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
index b7e3b5eea3f9..5dc5492a1fb5 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
@@ -522,26 +522,26 @@ static int etm_enable_sysfs(struct coresight_device *csdev, struct coresight_pat
 	struct etm_enable_arg arg = { };
 	int ret;
 
+	arg.drvdata = drvdata;
+	arg.traceid = path->trace_id;
+
+	raw_spin_lock(&drvdata->spinlock);
+	arg.config = drvdata->config;
+	raw_spin_unlock(&drvdata->spinlock);
 
 	/*
 	 * Configure the ETM only if the CPU is online.  If it isn't online
 	 * hw configuration will take place on the local CPU during bring up.
 	 */
-	if (cpu_online(drvdata->cpu)) {
-		arg.drvdata = drvdata;
-		arg.traceid = path->trace_id;
-
-		raw_spin_lock(&drvdata->spinlock);
-		arg.config = drvdata->config;
-		raw_spin_unlock(&drvdata->spinlock);
-
+	cpus_read_lock();
 		ret = smp_call_function_single(drvdata->cpu,
 					       etm_enable_sysfs_smp_call, &arg, 1);
-		if (!ret)
-			ret = arg.rc;
-	} else {
+	cpus_read_unlock();
+
+	if (!ret)
+		ret = arg.rc;
+	else
 		ret = -ENODEV;
-	}
 
 	if (!ret)
 		dev_dbg(&csdev->dev, "ETM tracing enabled\n");
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}