Re: [PATCH v3 9/9] coresight/ultrasoc: change cti_drvdata spinlock's type to raw_spinlock_t

Title of patch - this patch has nothing to do with cti_drvdata.

Mike

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

In ultrasoc-smb drivers, smb_drv_data->spinlock can be held during __schedule() by perf_event_task_sched_out()/in().

Since smb__drv_data->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 smb_drv_data->spinlock in ultrasoc-smb 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/ultrasoc-smb.c | 12 ++++++------ drivers/hwtracing/coresight/ultrasoc-smb.h | 2 +- 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c index dc3c9504dd7c..26cfc939e5bd 100644 --- a/drivers/hwtracing/coresight/ultrasoc-smb.c +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c @@ -98,7 +98,7 @@ static int smb_open(struct inode *inode, struct file *file) struct smb_drv_data *drvdata = container_of(file->private_data, struct smb_drv_data, miscdev);

•   guard(spinlock)(&drvdata->spinlock);
  

•   guard(raw_spinlock)(&drvdata->spinlock);
  
    if (drvdata->reading)
            return -EBUSY;
  

@@ -152,7 +152,7 @@ static int smb_release(struct inode *inode, struct file *file) struct smb_drv_data *drvdata = container_of(file->private_data, struct smb_drv_data, miscdev);

•   guard(spinlock)(&drvdata->spinlock);
  

•   guard(raw_spinlock)(&drvdata->spinlock);
    drvdata->reading = false;
  
    return 0;
  

@@ -245,7 +245,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode, struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent); int ret = 0;

•   guard(spinlock)(&drvdata->spinlock);
  

•   guard(raw_spinlock)(&drvdata->spinlock);
  
    /* Do nothing, the trace data is reading by other interface now */
    if (drvdata->reading)
  

@@ -280,7 +280,7 @@ static int smb_disable(struct coresight_device *csdev) { struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);

•   guard(spinlock)(&drvdata->spinlock);
  

•   guard(raw_spinlock)(&drvdata->spinlock);
  
    if (drvdata->reading)
            return -EBUSY;
  

@@ -378,7 +378,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev, if (!buf) return 0;

•   guard(spinlock)(&drvdata->spinlock);
  

•   guard(raw_spinlock)(&drvdata->spinlock);
  
    /* Don't do anything if another tracer is using this sink. */
    if (csdev->refcnt != 1)
  

@@ -563,7 +563,7 @@ static int smb_probe(struct platform_device *pdev)

    smb_reset_buffer(drvdata);
    platform_set_drvdata(pdev, drvdata);

•   spin_lock_init(&drvdata->spinlock);
  

•   raw_spin_lock_init(&drvdata->spinlock);
    drvdata->pid = -1;
  
    ret = smb_register_sink(pdev, drvdata);
  

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h index a91d39cfccb8..c4c111275627 100644 --- a/drivers/hwtracing/coresight/ultrasoc-smb.h +++ b/drivers/hwtracing/coresight/ultrasoc-smb.h @@ -115,7 +115,7 @@ struct smb_drv_data { struct coresight_device *csdev; struct smb_data_buffer sdb; struct miscdevice miscdev;

•   spinlock_t spinlock;
  

•   raw_spinlock_t spinlock;
    bool reading;
    pid_t pid;
  

};

LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

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