linux-kernel - [PATCH 6/9] coresight-funnel: change funnel_drvdata spinlock's type to raw_spinlock

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Message-Id: <20241125094816.365472-7-yeoreum.yun@arm.com>
Date: Mon, 25 Nov 2024 09:48:13 +0000
From: Yeoreum Yun <yeoreum.yun@....com>
To: suzuki.poulose@....com,
	mike.leach@...aro.org,
	james.clark@...aro.org,
	alexander.shishkin@...ux.intel.com,
	bigeasy@...utronix.de,
	clrkwllms@...nel.org,
	rostedt@...dmis.org
Cc: coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev,
	nd@....com,
	Levi Yun <yeoreum.yun@....com>
Subject: [PATCH 6/9] coresight-funnel: change funnel_drvdata spinlock's type to raw_spinlock_t

From: Levi Yun <yeoreum.yun@....com>

In coresight-funnel drivers, cti_drvdata->spinlock can be held
during __schedule() by perf_event_task_sched_out()/in().

Since funnel_drvdata->spinlock type is spinlock_t and
perf_event_task_sched_out()/in() is called after acquiring rq_lock,
which is raw_spinlock_t (an unsleepable lock),
this poses an issue in PREEMPT_RT kernel where spinlock_t is sleepable.

To address this, change type funnel_drvdata->spinlock in
coresight-funnel drivers, which can be called by
perf_event_task_sched_out()/in(), from spinlock_t to raw_spinlock_t.

Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
---
 .../hwtracing/coresight/coresight-funnel.c    | 34 +++++++++----------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
index 5a819c8970fb..dbc2891a10e1 100644
--- a/drivers/hwtracing/coresight/coresight-funnel.c
+++ b/drivers/hwtracing/coresight/coresight-funnel.c
@@ -47,7 +47,7 @@ struct funnel_drvdata {
 	struct clk		*pclk;
 	struct coresight_device	*csdev;
 	unsigned long		priority;
-	spinlock_t		spinlock;
+	raw_spinlock_t		spinlock;
 };
 
 static int dynamic_funnel_enable_hw(struct funnel_drvdata *drvdata, int port)
@@ -82,19 +82,18 @@ static int funnel_enable(struct coresight_device *csdev,
 {
 	int rc = 0;
 	struct funnel_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
-	unsigned long flags;
 	bool first_enable = false;
 
-	spin_lock_irqsave(&drvdata->spinlock, flags);
-	if (atomic_read(&in->dest_refcnt) == 0) {
-		if (drvdata->base)
-			rc = dynamic_funnel_enable_hw(drvdata, in->dest_port);
+	scoped_guard(raw_spinlock_irqsave, &drvdata->spinlock) {
+		if (atomic_read(&in->dest_refcnt) == 0) {
+			if (drvdata->base)
+				rc = dynamic_funnel_enable_hw(drvdata, in->dest_port);
+			if (!rc)
+				first_enable = true;
+		}
 		if (!rc)
-			first_enable = true;
+			atomic_inc(&in->dest_refcnt);
 	}
-	if (!rc)
-		atomic_inc(&in->dest_refcnt);
-	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	if (first_enable)
 		dev_dbg(&csdev->dev, "FUNNEL inport %d enabled\n",
@@ -126,16 +125,15 @@ static void funnel_disable(struct coresight_device *csdev,
 			   struct coresight_connection *out)
 {
 	struct funnel_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
-	unsigned long flags;
 	bool last_disable = false;
 
-	spin_lock_irqsave(&drvdata->spinlock, flags);
-	if (atomic_dec_return(&in->dest_refcnt) == 0) {
-		if (drvdata->base)
-			dynamic_funnel_disable_hw(drvdata, in->dest_port);
-		last_disable = true;
+	scoped_guard(raw_spinlock_irqsave, &drvdata->spinlock) {
+		if (atomic_dec_return(&in->dest_refcnt) == 0) {
+			if (drvdata->base)
+				dynamic_funnel_disable_hw(drvdata, in->dest_port);
+			last_disable = true;
+		}
 	}
-	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	if (last_disable)
 		dev_dbg(&csdev->dev, "FUNNEL inport %d disabled\n",
@@ -266,7 +264,7 @@ static int funnel_probe(struct device *dev, struct resource *res)
 	}
 	dev->platform_data = pdata;
 
-	spin_lock_init(&drvdata->spinlock);
+	raw_spin_lock_init(&drvdata->spinlock);
 	desc.type = CORESIGHT_DEV_TYPE_LINK;
 	desc.subtype.link_subtype = CORESIGHT_DEV_SUBTYPE_LINK_MERG;
 	desc.ops = &funnel_cs_ops;
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}