[PATCH v3 1/9] coresight: change coresight_device lock type to raw_spinlock_t

[Mike Leach]

On Mon, 16 Dec 2024 at 11:50, Yeoreum Yun <yeoreum.yun at arm.com> wrote:
>
> coresight_device->cscfg_csdev_lock can be held during __schedule()
> by perf_event_task_sched_out()/in().
>
> Since coresight->cscfg_csdev_lock 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 of coresight_device->cscfg_csdev_lock
> from spinlock_t to raw_spinlock_t.
>
> Signed-off-by: Yeoreum Yun <yeoreum.yun at arm.com>
> ---
>  .../hwtracing/coresight/coresight-syscfg.c    | 26 +++++++++----------
>  include/linux/coresight.h                     |  2 +-
>  2 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index 11138a9762b0..a70c1454b410 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -89,9 +89,9 @@ static int cscfg_add_csdev_cfg(struct coresight_device *csdev,
>         }
>         /* if matched features, add config to device.*/
>         if (config_csdev) {
> -               spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> +               raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
>                 list_add(&config_csdev->node, &csdev->config_csdev_list);
> -               spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> +               raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
>         }
>
>         return 0;
> @@ -194,9 +194,9 @@ static int cscfg_load_feat_csdev(struct coresight_device *csdev,
>
>         /* add to internal csdev feature list & initialise using reset call */
>         cscfg_reset_feat(feat_csdev);
> -       spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
>         list_add(&feat_csdev->node, &csdev->feature_csdev_list);
> -       spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
>
>         return 0;
>  }
> @@ -765,7 +765,7 @@ static int cscfg_list_add_csdev(struct coresight_device *csdev,
>
>         INIT_LIST_HEAD(&csdev->feature_csdev_list);
>         INIT_LIST_HEAD(&csdev->config_csdev_list);
> -       spin_lock_init(&csdev->cscfg_csdev_lock);
> +       raw_spin_lock_init(&csdev->cscfg_csdev_lock);
>
>         return 0;
>  }
> @@ -855,7 +855,7 @@ void cscfg_csdev_reset_feats(struct coresight_device *csdev)
>         struct cscfg_feature_csdev *feat_csdev;
>         unsigned long flags;
>
> -       spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
>         if (list_empty(&csdev->feature_csdev_list))
>                 goto unlock_exit;
>
> @@ -863,7 +863,7 @@ void cscfg_csdev_reset_feats(struct coresight_device *csdev)
>                 cscfg_reset_feat(feat_csdev);
>
>  unlock_exit:
> -       spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
>  }
>  EXPORT_SYMBOL_GPL(cscfg_csdev_reset_feats);
>
> @@ -1059,7 +1059,7 @@ int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
>          * Look for matching configuration - set the active configuration
>          * context if found.
>          */
> -       spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
>         list_for_each_entry(config_csdev_item, &csdev->config_csdev_list, node) {
>                 config_desc = config_csdev_item->config_desc;
>                 if ((atomic_read(&config_desc->active_cnt)) &&
> @@ -1069,7 +1069,7 @@ int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
>                         break;
>                 }
>         }
> -       spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
>
>         /*
>          * If found, attempt to enable
> @@ -1090,12 +1090,12 @@ int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
>                          *
>                          * Set enabled if OK, err if not.
>                          */
> -                       spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> +                       raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
>                         if (csdev->active_cscfg_ctxt)
>                                 config_csdev_active->enabled = true;
>                         else
>                                 err = -EBUSY;
> -                       spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> +                       raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
>                 }
>         }
>         return err;
> @@ -1124,7 +1124,7 @@ void cscfg_csdev_disable_active_config(struct coresight_device *csdev)
>          * If it was not enabled, we have no work to do, otherwise mark as disabled.
>          * Clear the active config pointer.
>          */
> -       spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);
>         config_csdev = (struct cscfg_config_csdev *)csdev->active_cscfg_ctxt;
>         if (config_csdev) {
>                 if (!config_csdev->enabled)
> @@ -1133,7 +1133,7 @@ void cscfg_csdev_disable_active_config(struct coresight_device *csdev)
>                         config_csdev->enabled = false;
>         }
>         csdev->active_cscfg_ctxt = NULL;
> -       spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
> +       raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);
>
>         /* true if there was an enabled active config */
>         if (config_csdev)
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> index c13342594278..924b58c343b3 100644
> --- a/include/linux/coresight.h
> +++ b/include/linux/coresight.h
> @@ -296,7 +296,7 @@ struct coresight_device {
>         /* system configuration and feature lists */
>         struct list_head feature_csdev_list;
>         struct list_head config_csdev_list;
> -       spinlock_t cscfg_csdev_lock;
> +       raw_spinlock_t cscfg_csdev_lock;
>         void *active_cscfg_ctxt;
>  };
>
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>

Reviewed-by: Mike Leach <mike.leach at linaro.org>

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