linux-kernel - Re: [PATCH v5 2/3] coresight: holding cscfg_csdev

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Message-ID: <20250514091509.GD26114@e132581.arm.com>
Date: Wed, 14 May 2025 10:15:09 +0100
From: Leo Yan <leo.yan@....com>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: suzuki.poulose@....com, mike.leach@...aro.org, james.clark@...aro.org,
	alexander.shishkin@...ux.intel.com, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/3] coresight: holding cscfg_csdev_lock while
 removing cscfg from csdev

On Tue, May 13, 2025 at 06:06:21PM +0100, Yeoreum Yun wrote:
> There'll be possible race scenario for coresight config:
> 
> CPU0                                          CPU1
> (perf enable)                                 load module
>                                               cscfg_load_config_sets()
>                                               activate config. // sysfs
>                                               (sys_active_cnt == 1)
> ...
> cscfg_csdev_enable_active_config()
>   lock(csdev->cscfg_csdev_lock)
>                                               deactivate config // sysfs
>                                               (sys_activec_cnt == 0)
>                                               cscfg_unload_config_sets()
>   <iterating config_csdev_list>               cscfg_remove_owned_csdev_configs()
>   // here load config activate by CPU1
>   unlock(csdev->cscfg_csdev_lock)
> 
> iterating config_csdev_list could be raced with config_csdev_list's
> entry delete.
> 
> To resolve this race , hold csdev->cscfg_csdev_lock() while
> cscfg_remove_owned_csdev_configs()
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
> Fixes: 02bd588e12df ("coresight: configuration: Update API to permit dynamic load/unload")
> ---
>  drivers/hwtracing/coresight/coresight-syscfg.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index a70c1454b410..5d194b9269f5 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -391,14 +391,17 @@ static void cscfg_owner_put(struct cscfg_load_owner_info *owner_info)
>  static void cscfg_remove_owned_csdev_configs(struct coresight_device *csdev, void *load_owner)
>  {
>  	struct cscfg_config_csdev *config_csdev, *tmp;
> +	unsigned long flags;
>  
>  	if (list_empty(&csdev->config_csdev_list))
>  		return;
>  
> +	raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags);

Could we use the format:

   guard(raw_spinlock_irqsave)(&csdev->cscfg_csdev_lock);

Sorry I did not mention this in the earlier review.  Otherwise:

Reviewed-by: Leo Yan <leo.yan@....com>

>  	list_for_each_entry_safe(config_csdev, tmp, &csdev->config_csdev_list, node) {
>  		if (config_csdev->config_desc->load_owner == load_owner)
>  			list_del(&config_csdev->node);
>  	}
> +	raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);


>  }
>  
>  static void cscfg_remove_owned_csdev_features(struct coresight_device *csdev, void *load_owner)
> -- 
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>