linux-kernel - [PATCH] PCI: fix recusive device locking

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Message-ID: <20240628193514.1680137-1-kbusch@meta.com>
Date: Fri, 28 Jun 2024 12:35:14 -0700
From: Keith Busch <kbusch@...a.com>
To: <linux-kernel@...r.kernel.org>, <bhelgaas@...gle.com>
CC: Keith Busch <kbusch@...nel.org>, Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH] PCI: fix recusive device locking

From: Keith Busch <kbusch@...nel.org>

If one of the bus' devices has subordinates, the recursive call locks
itself, so no need to lock the device before the recusion or it will
surely deadlock.

Fixes: dbc5b5c0d268f87 ("PCI: Add missing bridge lock to pci_bus_lock()"
Cc: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Keith Busch <kbusch@...nel.org>
---
 drivers/pci/pci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 46beaf1815fab..d9f357812b3c5 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5487,9 +5487,10 @@ static void pci_bus_lock(struct pci_bus *bus)
 
 	pci_dev_lock(bus->self);
 	list_for_each_entry(dev, &bus->devices, bus_list) {
-		pci_dev_lock(dev);
 		if (dev->subordinate)
 			pci_bus_lock(dev->subordinate);
+		else
+			pci_dev_lock(dev);
 	}
 }
 
@@ -5501,7 +5502,8 @@ static void pci_bus_unlock(struct pci_bus *bus)
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		if (dev->subordinate)
 			pci_bus_unlock(dev->subordinate);
-		pci_dev_unlock(dev);
+		else
+			pci_dev_unlock(dev);
 	}
 	pci_dev_unlock(bus->self);
 }
-- 
2.43.0