On Wed, 2012-09-12 at 20:33 +0800, Yijing Wang wrote:
> Fix a small race condition window between pci_bus_ops_pop() and
> pci_bus_set_ops() functions.
>
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
> ---
> drivers/pci/pcie/aer/aer_inject.c | 8 ++------
> 1 files changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/pcie/aer/aer_inject.c b/drivers/pci/pcie/aer/aer_inject.c
> index bd043db..69c2d77 100644
> --- a/drivers/pci/pcie/aer/aer_inject.c
> +++ b/drivers/pci/pcie/aer/aer_inject.c
> @@ -141,12 +141,11 @@ static struct pci_ops *__find_pci_bus_ops(struct pci_bus *bus)
> return NULL;
> }
>
> +/* inject_lock must be held before calling */
> static struct pci_bus_ops *pci_bus_ops_pop(void)
> {
> - unsigned long flags;
> struct pci_bus_ops *bus_ops = NULL;
>
> - spin_lock_irqsave(&inject_lock, flags);
> if (list_empty(&pci_bus_ops_list))
> bus_ops = NULL;
> else {
> @@ -154,7 +153,6 @@ static struct pci_bus_ops *pci_bus_ops_pop(void)
> list_del(lh);
> bus_ops = list_entry(lh, struct pci_bus_ops, list);
> }
> - spin_unlock_irqrestore(&inject_lock, flags);
> return bus_ops;
> }
>
> @@ -610,14 +608,12 @@ static void __exit aer_inject_exit(void)
> bus_unregister_notifier(&pci_bus_type, &aerinj_hp_notifier);
> misc_deregister(&aer_inject_device);
>
> + spin_lock_irqsave(&inject_lock, flags);
> while ((bus_ops = pci_bus_ops_pop())) {
> pci_bus_set_ops(bus_ops->bus, bus_ops->ops);
> kfree(bus_ops);
> }
>
> - clean_untracked_pci_aer_ops();
> -
> - spin_lock_irqsave(&inject_lock, flags);
> list_for_each_entry_safe(err, err_next, &einjected, list) {
> list_del(&err->list);
> kfree(err);
This may trigger a AB BA dead lock. In aer_inject_exit, the lock
sequence is:
inject_lock -> pci_lock
In pci config read/write path, the lock sequence is:
pci_lock -> inject_lock
With lockdep enabled, you may found warning on that.
Best Regards,
Huang YIng
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