linux-kernel - Re: [PATCH -next] iommu/dmar: silence RCU-list debugging warnings

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Date:   Sat, 7 Mar 2020 19:53:05 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Qian Cai <cai@....pw>, jroedel@...e.de
Cc:     baolu.lu@...ux.intel.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] iommu/dmar: silence RCU-list debugging warnings

Hi,

On 2020/3/6 4:15, Qian Cai wrote:
> Similar to the commit 02d715b4a818 ("iommu/vt-d: Fix RCU list debugging
> warnings"), there are several other places that call
> list_for_each_entry_rcu() outside of an RCU read side critical section
> but with dmar_global_lock held. Silence those false positives as well.
> 
>   drivers/iommu/intel-iommu.c:4288 RCU-list traversed in non-reader section!!
>   1 lock held by swapper/0/1:
>    #0: ffffffff935892c8 (dmar_global_lock){+.+.}, at: intel_iommu_init+0x1ad/0xb97
> 
>   drivers/iommu/dmar.c:366 RCU-list traversed in non-reader section!!
>   1 lock held by swapper/0/1:
>    #0: ffffffff935892c8 (dmar_global_lock){+.+.}, at: intel_iommu_init+0x125/0xb97
> 
>   drivers/iommu/intel-iommu.c:5057 RCU-list traversed in non-reader section!!
>   1 lock held by swapper/0/1:
>    #0: ffffffffa71892c8 (dmar_global_lock){++++}, at: intel_iommu_init+0x61a/0xb13
> 
> Signed-off-by: Qian Cai <cai@....pw>


Thanks for the fix.

Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>

Best regards,
baolu

> ---
>   drivers/iommu/dmar.c | 3 ++-
>   include/linux/dmar.h | 6 ++++--
>   2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> index 071bb42bbbc5..7b16c4db40b4 100644
> --- a/drivers/iommu/dmar.c
> +++ b/drivers/iommu/dmar.c
> @@ -363,7 +363,8 @@ static int dmar_pci_bus_notifier(struct notifier_block *nb,
>   {
>   	struct dmar_drhd_unit *dmaru;
>   
> -	list_for_each_entry_rcu(dmaru, &dmar_drhd_units, list)
> +	list_for_each_entry_rcu(dmaru, &dmar_drhd_units, list,
> +				dmar_rcu_check())
>   		if (dmaru->segment == drhd->segment &&
>   		    dmaru->reg_base_addr == drhd->address)
>   			return dmaru;
> diff --git a/include/linux/dmar.h b/include/linux/dmar.h
> index 712be8bc6a7c..d7bf029df737 100644
> --- a/include/linux/dmar.h
> +++ b/include/linux/dmar.h
> @@ -74,11 +74,13 @@ struct dmar_pci_notify_info {
>   				dmar_rcu_check())
>   
>   #define for_each_active_drhd_unit(drhd)					\
> -	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)		\
> +	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list,		\
> +				dmar_rcu_check())			\
>   		if (drhd->ignored) {} else
>   
>   #define for_each_active_iommu(i, drhd)					\
> -	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)		\
> +	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list,		\
> +				dmar_rcu_check())			\
>   		if (i=drhd->iommu, drhd->ignored) {} else
>   
>   #define for_each_iommu(i, drhd)						\
>