2023-03-28 08:46:49

by Jürgen Groß

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 <[email protected]>
Link: https://lore.kernel.org/lkml/Y+JUIl64UDmdkboh@kadam/
Signed-off-by: Juergen Gross <[email protected]>
---
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

2023-03-28 11:49:58

by Oleksandr Tyshchenko

Subject: Re: [PATCH] xen/pciback: don't call pcistub_device_put() under lock

On 28.03.23 11:45, Juergen Gross wrote:

Hello Juergen

> 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 <[email protected]>
> Link: https://urldefense.com/v3/__https://lore.kernel.org/lkml/Y*JUIl64UDmdkboh@kadam/__;Kw!!GF_29dbcQIUBPA!wO4HR1jCrDMOfB1Ih2qEZs2jnqcieZUZnc6cPwh7Ta8hiLRKwS1Gs-1tmQP-NuEYoz9LhYWI8aFazIwIa8Lh$ [lore[.]kernel[.]org]
> Signed-off-by: Juergen Gross <[email protected]>


Reviewed-by: Oleksandr Tyshchenko <[email protected]>

> ---
> 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;
> }