linux-kernel - [PATCH] PCI: endpoint: Use blocking notifier instead of atomic

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Date:   Mon, 28 Feb 2022 11:01:59 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     kishon@...com, lorenzo.pieralisi@....com
Cc:     kw@...ux.com, bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, bjorn.andersson@...aro.org,
        dmitry.baryshkov@...aro.org,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH] PCI: endpoint: Use blocking notifier instead of atomic

The use of atomic notifier causes sleeping in atomic context bug when
the EPC core functions are used in the notifier chain. This is due to the
use of epc->lock (mutex) in core functions protecting the concurrent use of
EPC.

So switch to blocking notifier for getting rid of the bug as it runs in
non-atomic context and allows sleeping in notifier chain.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/endpoint/pci-epc-core.c | 10 +++++-----
 include/linux/pci-epc.h             |  6 +++---
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 6120d99bff73..6ad9b38b63a9 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -693,7 +693,7 @@ void pci_epc_linkup(struct pci_epc *epc)
 	if (!epc || IS_ERR(epc))
 		return;
 
-	atomic_notifier_call_chain(&epc->notifier, LINK_UP, NULL);
+	blocking_notifier_call_chain(&epc->notifier, LINK_UP, NULL);
 }
 EXPORT_SYMBOL_GPL(pci_epc_linkup);
 
@@ -710,7 +710,7 @@ void pci_epc_linkdown(struct pci_epc *epc)
 	if (!epc || IS_ERR(epc))
 		return;
 
-	atomic_notifier_call_chain(&epc->notifier, LINK_DOWN, NULL);
+	blocking_notifier_call_chain(&epc->notifier, LINK_DOWN, NULL);
 }
 EXPORT_SYMBOL_GPL(pci_epc_linkdown);
 
@@ -727,7 +727,7 @@ void pci_epc_init_notify(struct pci_epc *epc)
 	if (!epc || IS_ERR(epc))
 		return;
 
-	atomic_notifier_call_chain(&epc->notifier, CORE_INIT, NULL);
+	blocking_notifier_call_chain(&epc->notifier, CORE_INIT, NULL);
 }
 EXPORT_SYMBOL_GPL(pci_epc_init_notify);
 
@@ -744,7 +744,7 @@ void pci_epc_bme_notify(struct pci_epc *epc)
 	if (!epc || IS_ERR(epc))
 		return;
 
-	atomic_notifier_call_chain(&epc->notifier, BME, NULL);
+	blocking_notifier_call_chain(&epc->notifier, BME, NULL);
 }
 EXPORT_SYMBOL_GPL(pci_epc_bme_notify);
 
@@ -808,7 +808,7 @@ __pci_epc_create(struct device *dev, const struct pci_epc_ops *ops,
 
 	mutex_init(&epc->lock);
 	INIT_LIST_HEAD(&epc->pci_epf);
-	ATOMIC_INIT_NOTIFIER_HEAD(&epc->notifier);
+	BLOCKING_INIT_NOTIFIER_HEAD(&epc->notifier);
 
 	device_initialize(&epc->dev);
 	epc->dev.class = pci_epc_class;
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index 8454610df4c3..7a5c7705f86f 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -149,7 +149,7 @@ struct pci_epc {
 	/* mutex to protect against concurrent access of EP controller */
 	struct mutex			lock;
 	unsigned long			function_num_map;
-	struct atomic_notifier_head	notifier;
+	struct blocking_notifier_head	notifier;
 };
 
 /**
@@ -195,13 +195,13 @@ static inline void *epc_get_drvdata(struct pci_epc *epc)
 static inline int
 pci_epc_register_notifier(struct pci_epc *epc, struct notifier_block *nb)
 {
-	return atomic_notifier_chain_register(&epc->notifier, nb);
+	return blocking_notifier_chain_register(&epc->notifier, nb);
 }
 
 static inline int
 pci_epc_unregister_notifier(struct pci_epc *epc, struct notifier_block *nb)
 {
-	return atomic_notifier_chain_unregister(&epc->notifier, nb);
+	return blocking_notifier_chain_unregister(&epc->notifier, nb);
 }
 
 struct pci_epc *
-- 
2.25.1