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iommu: dmar: Fix RCU list debugging warnings

PATCH RESEND Applied Amol Grover 3 participants 3 messages Feb 23, 2020 – Mar 2, 2020

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Amol Grover

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#0 lore raw

PATCH RESEND 1/1 iommu: dmar: Fix RCU list debugging warnings

dmar_drhd_units is traversed using list_for_each_entry_rcu() outside of an RCU read side critical section but under the protection of dmar_global_lock. Hence add corresponding lockdep expression to silence the following false-positive warnings:

[    1.603975] =============================
[    1.603976] WARNING: suspicious RCU usage
[    1.603977] 5.5.4-stable #17 Not tainted
[    1.603978] -----------------------------
[    1.603980] drivers/iommu/intel-iommu.c:4769 RCU-list traversed in non-reader section!!
[    1.603869] =============================
[    1.603870] WARNING: suspicious RCU usage
[    1.603872] 5.5.4-stable #17 Not tainted
[    1.603874] -----------------------------
[    1.603875] drivers/iommu/dmar.c:293 RCU-list traversed in non-reader section!!
Tested-by Madhuparna Bhowmik <[email protected]>
Signed-off-by Amol Grover <[email protected]>
---
 include/linux/dmar.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
include/linux/dmar.h +5 -3
index f64ca27dc210..712be8bc6a7c 100644
@@ -69,8 +69,9 @@ struct dmar_pci_notify_info {
 extern struct rw_semaphore dmar_global_lock;
 extern struct list_head dmar_drhd_units;
 
-#define for_each_drhd_unit(drhd) \
-	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)
+#define for_each_drhd_unit(drhd)					\
+	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list,		\
+				dmar_rcu_check())
 
 #define for_each_active_drhd_unit(drhd)					\
 	list_for_each_entry_rcu(drhd, &dmar_drhd_units, list)		\

@@ -81,7 +82,8 @@ extern struct list_head dmar_drhd_units;
 		if (i=drhd->iommu, drhd->ignored) {} else
 
 #define for_each_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, 0) {} else 
 
 static inline bool dmar_rcu_check(void)
Signature · 6 lines
2.24.1

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Acked-by on v1 1/1
#1 lore raw
Quoted 11 lines · Amol Grover

dmar_drhd_units is traversed using list_for_each_entry_rcu() outside of an RCU read side critical section but under the protection of dmar_global_lock. Hence add corresponding lockdep expression to silence the following false-positive warnings:

[    1.603975] =============================
[    1.603976] WARNING: suspicious RCU usage
[    1.603977] 5.5.4-stable #17 Not tainted
[    1.603978] -----------------------------
[    1.603980] drivers/iommu/intel-iommu.c:4769 RCU-list traversed in non-reader section!!
Quoted 8 lines
[    1.603869] =============================
[    1.603870] WARNING: suspicious RCU usage
[    1.603872] 5.5.4-stable #17 Not tainted
[    1.603874] -----------------------------
[    1.603875] drivers/iommu/dmar.c:293 RCU-list traversed in non-reader section!!
Tested-by Madhuparna Bhowmik <[email protected]>
Signed-off-by Amol Grover <[email protected]>

Thanks for the fix.

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

Best regards,
baolu
_______________________________________________
Linux-kernel-mentees mailing list
[email protected]
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

Applied
#2 lore raw
In reply to Amol Grover
Quoted 17 lines · Amol Grover

dmar_drhd_units is traversed using list_for_each_entry_rcu() outside of an RCU read side critical section but under the protection of dmar_global_lock. Hence add corresponding lockdep expression to silence the following false-positive warnings:

[    1.603975] =============================
[    1.603976] WARNING: suspicious RCU usage
[    1.603977] 5.5.4-stable #17 Not tainted
[    1.603978] -----------------------------
[    1.603980] drivers/iommu/intel-iommu.c:4769 RCU-list traversed in non-reader section!!
[    1.603869] =============================
[    1.603870] WARNING: suspicious RCU usage
[    1.603872] 5.5.4-stable #17 Not tainted
[    1.603874] -----------------------------
[    1.603875] drivers/iommu/dmar.c:293 RCU-list traversed in non-reader section!!
Quoted 5 lines
Tested-by Madhuparna Bhowmik <[email protected]>
Signed-off-by Amol Grover <[email protected]>
---
 include/linux/dmar.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Applied, thanks.