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Message-Id: <20200222170333.10570-1-frextrite@gmail.com>
Date: Sat, 22 Feb 2020 22:33:33 +0530
From: Amol Grover <frextrite@...il.com>
To: Allison Randal <allison@...utok.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Lu Baolu <baolu.lu@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>, Qian Cai <cai@....pw>,
Deepa Dinamani <deepa.kernel@...il.com>
Cc: linux-kernel@...r.kernel.org,
linux-kernel-mentees@...ts.linuxfoundation.org,
Joel Fernandes <joel@...lfernandes.org>,
Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
"Paul E . McKenney" <paulmck@...nel.org>,
Amol Grover <frextrite@...il.com>
Subject: [PATCH] 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 <madhuparnabhowmik10@...il.com>
Signed-off-by: Amol Grover <frextrite@...il.com>
---
include/linux/dmar.h | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index f64ca27dc210..712be8bc6a7c 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -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)
--
2.24.1
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