Re: [PATCH v3 6/9] coresight-funnel: change funnel_drvdata spinlock's type to raw_spinlock_t

On Mon, 16 Dec 2024 at 11:50, Yeoreum Yun yeoreum.yun@arm.com wrote:

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@arm.com

drivers/hwtracing/coresight/coresight-funnel.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c index 33efe1acbef7..a566c8854327 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) @@ -85,7 +85,7 @@ static int funnel_enable(struct coresight_device *csdev, unsigned long flags; bool first_enable = false;

•   spin_lock_irqsave(&drvdata->spinlock, flags);
  

•   raw_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);
  

@@ -94,7 +94,7 @@ static int funnel_enable(struct coresight_device *csdev, } if (!rc) atomic_inc(&in->dest_refcnt);

•   spin_unlock_irqrestore(&drvdata->spinlock, flags);
  

•   raw_spin_unlock_irqrestore(&drvdata->spinlock, flags);
  
    if (first_enable)
            dev_dbg(&csdev->dev, "FUNNEL inport %d enabled\n",
  

@@ -129,13 +129,13 @@ static void funnel_disable(struct coresight_device *csdev, unsigned long flags; bool last_disable = false;

•   spin_lock_irqsave(&drvdata->spinlock, flags);
  

•   raw_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;
    }
  

•   spin_unlock_irqrestore(&drvdata->spinlock, flags);
  

•   raw_spin_unlock_irqrestore(&drvdata->spinlock, flags);
  
    if (last_disable)
            dev_dbg(&csdev->dev, "FUNNEL inport %d disabled\n",
  

@@ -266,7 +266,7 @@ 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}

Reviewed-by: Mike Leach mike.leach@linaro.org

-- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK