On Fri, Apr 6, 2012 at 9:31 AM, Jiang Liu <liuj97@xxxxxxxxx> wrote:
> Function pci_get_dev_by_id() will hold a reference count on the pci device
> returned, so pci_dev_present() should release the corresponding reference
> count to avoid memory leakage.
>
> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
> ---
> drivers/pci/search.c | 10 +++++-----
> 1 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> index 9d75dc8..b572730 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -338,13 +338,13 @@ int pci_dev_present(const struct pci_device_id *ids)
> WARN_ON(in_interrupt());
> while (ids->vendor || ids->subvendor || ids->class_mask) {
> found = pci_get_dev_by_id(ids, NULL);
> - if (found)
> - goto exit;
> + if (found) {
> + pci_dev_put(found);
> + return 1;
> + }
> ids++;
> }
> -exit:
> - if (found)
> - return 1;
> +
> return 0;
> }
> EXPORT_SYMBOL(pci_dev_present);
This might be the right thing to do, but I'd like to understand what's
going on, so let's talk about it a bit first.
I agree, there appears to be a leak here. Or at least, the fact that
we keep a reference when a device is found doesn't match the comment.
What problem are you seeing from this leak?
There are not many callers, and most appear to be one-time things done
at boot, looking for built-in devices known to be defective. These
devices won't be removable, so the leak shouldn't be causing
hot-remove issues.
IMO, this is a bogus interface that leads to poor code, and I don't
want to encourage its use. For device defect workarounds, I think
it'd be better to use PCI quirks to catch the defective device. Some
chipset defects affect all downstream devices, and a quirk could make
the defect visible to all the drivers, not just the ones that use
pci_dev_present(). For example, look at tg3_write_reorder_chipsets
and tg3_dma_wait_state_chipsets. Those aren't for tg3 bugs, they're
for chipset bugs that might affect other devices, too. But right now,
that knowledge is buried in the tg3 driver.
Bjorn
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