Re: [PATCH v7 08/20] coresight: syscfg: Use spinlock to protect active variables

On 20/03/2026 17:42, Leo Yan wrote:

To support dynamically enabling and disabling the CoreSight path during CPU idle, cscfg_config_sysfs_get_active_cfg() may be called by the ETM driver in an atomic context. However, the function currently acquires a mutex, which is a sleepable lock, and this is not allowed in atomic context.

To make cscfg_config_sysfs_get_active_cfg() called in the idle flow, replace the mutex with a raw spinlock to protect the active variables.

Reviewed-by: James Clark james.clark@linaro.org Tested-by: James Clark james.clark@linaro.org Reviewed-by: Yeoreum Yun yeoreum.yun@arm.com Signed-off-by: Leo Yan leo.yan@arm.com

---

drivers/hwtracing/coresight/coresight-syscfg.c | 21 ++++++++++++--------- drivers/hwtracing/coresight/coresight-syscfg.h | 2 ++ 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index d7f5037953d6ba7fb7f83a8012a1abc5ffd0a147..3b77e4da6b6b3cfc0aa687c0280c8ee5118e286b 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -957,15 +957,18 @@ int cscfg_config_sysfs_activate(struct cscfg_config_desc *config_desc, bool acti cfg_hash = (unsigned long)config_desc->event_ea->var;

• raw_spin_lock(&cscfg_mgr->spinlock);
• if (activate) { /* cannot be a current active value to activate this */ if (cscfg_mgr->sysfs_active_config) { err = -EBUSY;

• 	goto exit_unlock;
  

• } else {
  

• 	err = _cscfg_activate_config(cfg_hash);
  

• 	if (!err)
  

• 		cscfg_mgr->sysfs_active_config = cfg_hash;
  

  }

• err = _cscfg_activate_config(cfg_hash);
  

• if (!err)
  

• 	cscfg_mgr->sysfs_active_config = cfg_hash;
  

• } else { /* disable if matching current value */ if (cscfg_mgr->sysfs_active_config == cfg_hash) {

@@ -975,7 +978,8 @@ int cscfg_config_sysfs_activate(struct cscfg_config_desc *config_desc, bool acti err = -EINVAL; } -exit_unlock:

• raw_spin_unlock(&cscfg_mgr->spinlock);
• mutex_unlock(&cscfg_mutex); return err; }

@@ -983,9 +987,8 @@ int cscfg_config_sysfs_activate(struct cscfg_config_desc *config_desc, bool acti /* set the sysfs preset value */ void cscfg_config_sysfs_set_preset(int preset) {

• mutex_lock(&cscfg_mutex);

• guard(raw_spinlock)(&cscfg_mgr->spinlock); cscfg_mgr->sysfs_active_preset = preset;

• mutex_unlock(&cscfg_mutex); }

/* @@ -994,10 +997,9 @@ void cscfg_config_sysfs_set_preset(int preset) */ void cscfg_config_sysfs_get_active_cfg(unsigned long *cfg_hash, int *preset) {

• mutex_lock(&cscfg_mutex);

• guard(raw_spinlock)(&cscfg_mgr->spinlock); *preset = cscfg_mgr->sysfs_active_preset; *cfg_hash = cscfg_mgr->sysfs_active_config;

• mutex_unlock(&cscfg_mutex); } EXPORT_SYMBOL_GPL(cscfg_config_sysfs_get_active_cfg);

@@ -1201,6 +1203,7 @@ static int cscfg_create_device(void) INIT_LIST_HEAD(&cscfg_mgr->load_order_list); atomic_set(&cscfg_mgr->sys_active_cnt, 0); cscfg_mgr->load_state = CSCFG_NONE;

• raw_spin_lock_init(&cscfg_mgr->spinlock);

/* setup the device */ dev = cscfg_device(); diff --git a/drivers/hwtracing/coresight/coresight-syscfg.h b/drivers/hwtracing/coresight/coresight-syscfg.h index 66e2db890d8203853a0c3c907b48aa66dd8014e6..f52aba4608dadc1c7666e0e28c9b43dc1c33d1eb 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.h +++ b/drivers/hwtracing/coresight/coresight-syscfg.h @@ -42,6 +42,7 @@ enum cscfg_load_ops {

• @sysfs_active_config:Active config hash used if CoreSight controlled from sysfs.
• @sysfs_active_preset:Active preset index used if CoreSight controlled from sysfs.
• @load_state: A multi-stage load/unload operation is in progress.

• • @spinlock: Exclusive access sysfs_active_* variables.

minor nit: s/spinlock/sysfs_store_lock to make it explicit in the code and we don't have to look up what this protects ?

Suzuki

*/ struct cscfg_manager { struct device dev; @@ -54,6 +55,7 @@ struct cscfg_manager { u32 sysfs_active_config; int sysfs_active_preset; enum cscfg_load_ops load_state;

• raw_spinlock_t spinlock; };

/* get reference to dev in cscfg_manager */