Hi Mike.

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

Sorry. I'll fix this. Thanks

On Mon, 16 Dec 2024 at 11:50, Yeoreum Yun [off-list ref] wrote:

quoted

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 <redacted>
---
 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