Re: [PATCH] drm/i915/gt: debugfs: Evaluate forcewake usage within locks

[Nirmoy Das <nirmoy.das@linux.intel.com>]

Hi Andi,

On 6/7/2024 4:51 PM, Andi Shyti wrote:
> The forcewake count and domains listing is multi process critical
> and the uncore provides a spinlock for such cases.
>
> Lock the forcewake evaluation section in the fw_domains_show()
> debugfs interface.
>
> Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>

Needs a Fixes tag, below seems to be correct one.


Fixes: 9dd4b065446a ("drm/i915/gt: Move pm debug files into a gt aware 
debugfs")

Cc: <stable@vger.kernel.org> # v5.6+

Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>


Regards,

Nirmoy


> ---
>   drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c b/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c
> index 4fcba42cfe34..0437fd8217e0 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm_debugfs.c
> @@ -71,6 +71,8 @@ static int fw_domains_show(struct seq_file *m, void *data)
>   	struct intel_uncore_forcewake_domain *fw_domain;
>   	unsigned int tmp;
>   
> +	spin_lock_irq(&uncore->lock);
> +
>   	seq_printf(m, "user.bypass_count = %u\n",
>   		   uncore->user_forcewake_count);
>   
> @@ -79,6 +81,8 @@ static int fw_domains_show(struct seq_file *m, void *data)
>   			   intel_uncore_forcewake_domain_to_str(fw_domain->id),
>   			   READ_ONCE(fw_domain->wake_count));
>   
> +	spin_unlock_irq(&uncore->lock);
> +
>   	return 0;
>   }
>   DEFINE_INTEL_GT_DEBUGFS_ATTRIBUTE(fw_domains);