Re: [PATCH v3 7/9] coresight-replicator: change replicator_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-replicator drivers, replicator_drvdata->spinlock can be held during __schedule() by perf_event_task_sched_out()/in().

Since replicator_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 replicator_drvdata->spinlock in coresight-replicator 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-replicator.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-replicator.c b/drivers/hwtracing/coresight/coresight-replicator.c index 0fba87de6d1a..7d36fe2176cc 100644 --- a/drivers/hwtracing/coresight/coresight-replicator.c +++ b/drivers/hwtracing/coresight/coresight-replicator.c @@ -41,7 +41,7 @@ struct replicator_drvdata { struct clk *atclk; struct clk *pclk; struct coresight_device *csdev;

•   spinlock_t              spinlock;
  

•   raw_spinlock_t          spinlock;
    bool                    check_idfilter_val;
  

};

@@ -125,7 +125,7 @@ static int replicator_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(&out->src_refcnt) == 0) {
            if (drvdata->base)
                    rc = dynamic_replicator_enable(drvdata, in->dest_port,
  

@@ -135,7 +135,7 @@ static int replicator_enable(struct coresight_device *csdev, } if (!rc) atomic_inc(&out->src_refcnt);

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

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

@@ -179,14 +179,14 @@ static void replicator_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(&out->src_refcnt) == 0) {
            if (drvdata->base)
                    dynamic_replicator_disable(drvdata, in->dest_port,
                                               out->src_port);
            last_disable = true;
    }
  

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

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

@@ -277,7 +277,7 @@ static int replicator_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_SPLIT;
    desc.ops = &replicator_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