linux-kernel - [PATCH] xen/pciback: don't call pcistub_device

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Date:   Tue, 28 Mar 2023 10:45:49 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        xen-devel@...ts.xenproject.org, Dan Carpenter <error27@...il.com>
Subject: [PATCH] xen/pciback: don't call pcistub_device_put() under lock

pcistub_device_put() shouldn't be called under spinlock, as it can
sleep.

For this reason pcistub_device_get_pci_dev() needs to be modified:
instead of always calling pcistub_device_get() just do the call of
pcistub_device_get() only if it is really needed. This removes the
need to call pcistub_device_put().

Reported-by: Dan Carpenter <error27@...il.com>
Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 drivers/xen/xen-pciback/pci_stub.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index bba527620507..e34b623e4b41 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -194,8 +194,6 @@ static struct pci_dev *pcistub_device_get_pci_dev(struct xen_pcibk_device *pdev,
 	struct pci_dev *pci_dev = NULL;
 	unsigned long flags;
 
-	pcistub_device_get(psdev);
-
 	spin_lock_irqsave(&psdev->lock, flags);
 	if (!psdev->pdev) {
 		psdev->pdev = pdev;
@@ -203,8 +201,8 @@ static struct pci_dev *pcistub_device_get_pci_dev(struct xen_pcibk_device *pdev,
 	}
 	spin_unlock_irqrestore(&psdev->lock, flags);
 
-	if (!pci_dev)
-		pcistub_device_put(psdev);
+	if (pci_dev)
+		pcistub_device_get(psdev);
 
 	return pci_dev;
 }
-- 
2.35.3