On 2012/9/13 9:29, Huang Ying wrote:
> 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.
OK, I will carry out a detailed test with lockdep enabled, and try to improve this patch.
Thanks for review and comments!
------
Thanks
Yijing
>
> Best Regards,
> Huang YIng
>
>
>
> .
>
--
Thanks!
Yijing
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