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

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Message-ID: <aCR63YGVjWe+L3mR@e129823.arm.com>
Date: Wed, 14 May 2025 12:13:33 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: Leo Yan <leo.yan@....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

Hi Leo,

> 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);

No problem. I'll convert with guard.

> Sorry I did not mention this in the earlier review.  Otherwise:
>
> Reviewed-by: Leo Yan <leo.yan@....com>

Thanks :)
>
> >  	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}
> >

--
Sincerely,
Yeoreum Yun