On Wed, Apr 22, 2026 at 02:21:58PM +0100, Yeoreum Yun wrote:

[...]

• /*

• * Take the hotplug lock to prevent redundant calls to etm4_enable_hw().
  

• *
  

• * The cpu_online_mask is set at the CPUHP_BRINGUP_CPU step.
  

• * In other words, if etm4_enable_sysfs() is called between
  

• * CPUHP_BRINGUP_CPU and CPUHP_AP_ARM_CORESIGHT_STARTING,
  

• * etm4_enable_hw() may be invoked in etm4_enable_sysfs_smp_call()
  

• * and then executed again in etm4_starting_cpu().
  

• */
  

• cpus_read_lock(); ret = smp_call_function_single(drvdata->cpu, etm4_enable_sysfs_smp_call, &arg, 1);
• cpus_read_unlock();

This will cause double deadlock with the patch: https://lore.kernel.org/linux-arm-kernel/20260511-arm_coresight_path_power_m...

I think we need to drop this one.

Thanks, Leo