Re: [PATCH v4 2/2] coresight: Fix possible deadlock in coresight_panic_cb

On Fri, Sep 19, 2025 at 12:06:53PM -0400, Sean Anderson wrote:

[...]

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index 022c8384b98d..6dfb1198c16e 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -1046,8 +1046,11 @@ static void coresight_device_release(struct device *dev) { struct coresight_device *csdev = to_coresight_device(dev);

• fwnode_handle_put(csdev->dev.fwnode);

• if (panic_ops(csdev))

• atomic_notifier_chain_unregister(&panic_notifier_list,
  

• 				 &csdev->panic_notifier);
  

  free_percpu(csdev->perf_sink_id_map.cpu_map);
• fwnode_handle_put(csdev->dev.fwnode);

The moving fwnode_handle_put() is irrelvant to panic notifier fix, should be moved out from this patch.

kfree(csdev); } @@ -1315,6 +1318,16 @@ void coresight_release_platform_data(struct coresight_device *csdev, coresight_remove_conns_sysfs_group(csdev); } +static int coresight_panic_notifier(struct notifier_block *nb,

• 		    unsigned long action, void *data)
  

+{

• struct coresight_device *csdev =

• container_of(nb, struct coresight_device, panic_notifier);
  

Need to check device mode:

if (coresight_get_mode(csdev) == CS_MODE_DISABLED) return NOTIFY_DONE;

The rest is fine for me.

Thanks, Leo

• panic_ops(csdev)->sync(csdev);
• return NOTIFY_DONE;

+}

struct coresight_device *coresight_register(struct coresight_desc *desc) { int ret; @@ -1357,6 +1370,17 @@ struct coresight_device *coresight_register(struct coresight_desc *desc) goto err_out; } }

• if (panic_ops(csdev)) {

• csdev->panic_notifier.notifier_call = coresight_panic_notifier;
  

• ret = atomic_notifier_chain_register(&panic_notifier_list,
  

• 				     &csdev->panic_notifier);
  

• if (ret) {
  

• 	coresight_device_release(&csdev->dev);
  

• 	goto err_out;
  

• }
  

• }
• /*
  • Make sure the device registration and the connection fixup
  • are synchronised, so that we don't see uninitialised devices

@@ -1563,36 +1587,6 @@ const struct bus_type coresight_bustype = { .name = "coresight", }; -static int coresight_panic_sync(struct device *dev, void *data) -{

• int mode;
• struct coresight_device *csdev;
• /* Run through panic sync handlers for all enabled devices */
• csdev = container_of(dev, struct coresight_device, dev);
• mode = coresight_get_mode(csdev);
• if ((mode == CS_MODE_SYSFS) || (mode == CS_MODE_PERF)) {

• if (panic_ops(csdev))
  

• 	panic_ops(csdev)->sync(csdev);
  

• }
• return 0;

-}

-static int coresight_panic_cb(struct notifier_block *self,

• 	       unsigned long v, void *p)
  

-{

• bus_for_each_dev(&coresight_bustype, NULL, NULL,

• 		 coresight_panic_sync);
  

• return 0;

-}

-static struct notifier_block coresight_notifier = {

• .notifier_call = coresight_panic_cb,

-};

static int __init coresight_init(void) { int ret; @@ -1605,20 +1599,11 @@ static int __init coresight_init(void) if (ret) goto exit_bus_unregister;

• /* Register function to be called for panic */
• ret = atomic_notifier_chain_register(&panic_notifier_list,

• 			     &coresight_notifier);
  

• if (ret)

• goto exit_perf;
  

• /* initialise the coresight syscfg API */ ret = cscfg_init(); if (!ret) return 0;

• atomic_notifier_chain_unregister(&panic_notifier_list,

• 			     &coresight_notifier);
  

-exit_perf: etm_perf_exit(); exit_bus_unregister: bus_unregister(&coresight_bustype); @@ -1628,8 +1613,6 @@ static int __init coresight_init(void) static void __exit coresight_exit(void) { cscfg_exit();

• atomic_notifier_chain_unregister(&panic_notifier_list,

• 			     &coresight_notifier);
  

  etm_perf_exit(); bus_unregister(&coresight_bustype);

} diff --git a/include/linux/coresight.h b/include/linux/coresight.h index 4ac65c68bbf4..a7aaf9d3d01d 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -280,6 +280,7 @@ struct coresight_trace_id_map {

• @config_csdev_list: List of system configurations added to the device.
• @cscfg_csdev_lock: Protect the lists of configurations and features.
• @active_cscfg_ctxt: Context information for current active system configuration.

• • @panic_notifier: Notifier block used to clean up during a panic
  */

struct coresight_device { struct coresight_platform_data *pdata; @@ -304,6 +305,7 @@ struct coresight_device { struct list_head config_csdev_list; raw_spinlock_t cscfg_csdev_lock; void *active_cscfg_ctxt;

• struct notifier_block panic_notifier;

}; /* -- 2.35.1.1320.gc452695387.dirty