2020-03-05 20:16:17

by Qian Cai

Subject: [PATCH -next] iommu/dmar: silence RCU-list debugging warnings

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 <[email protected]>
---
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) \
--
1.8.3.1

2020-03-07 11:54:03

by Lu Baolu

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 <[email protected]>


Thanks for the fix.

Acked-by: Lu Baolu <[email protected]>

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) \
>

2020-03-10 09:33:13

by Jörg Rödel

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

On Thu, Mar 05, 2020 at 03:15:02PM -0500, Qian Cai wrote:
> drivers/iommu/dmar.c | 3 ++-
> include/linux/dmar.h | 6 ++++--
> 2 files changed, 6 insertions(+), 3 deletions(-)

Applied, thanks.