[dpdk-dev] [PATCH v3 2/5] bus/vdev: add lock on vdev device list
Burakov, Anatoly
anatoly.burakov at intel.com
Fri Apr 20 17:16:38 CEST 2018
On 20-Apr-18 3:19 PM, Tan, Jianfeng wrote:
>
>
> On 4/20/2018 4:26 PM, Burakov, Anatoly wrote:
>> On 19-Apr-18 5:50 PM, Jianfeng Tan wrote:
>>> As we could add virtual devices from different threads now, we
>>> add a spin lock to protect the vdev device list.
>>>
>>> Suggested-by: Anatoly Burakov <anatoly.burakov at intel.com>
>>> Signed-off-by: Jianfeng Tan <jianfeng.tan at intel.com>
>>> Reviewed-by: Qi Zhang <qi.z.zhang at intel.com>
>>> ---
>>
>> <...>
>>
>>> +/* The caller shall be responsible for thread-safe */
>>> static struct rte_vdev_device *
>>> find_vdev(const char *name)
>>> {
>>> @@ -203,10 +206,6 @@ rte_vdev_init(const char *name, const char *args)
>>> if (name == NULL)
>>> return -EINVAL;
>>> - dev = find_vdev(name);
>>> - if (dev)
>>> - return -EEXIST;
>>> -
>>> devargs = alloc_devargs(name, args);
>>> if (!devargs)
>>> return -ENOMEM;
>>> @@ -221,16 +220,28 @@ rte_vdev_init(const char *name, const char *args)
>>> dev->device.numa_node = SOCKET_ID_ANY;
>>> dev->device.name = devargs->name;
>>> + rte_spinlock_lock(&vdev_device_list_lock);
>>> + if (find_vdev(name)) {
>>> + rte_spinlock_unlock(&vdev_device_list_lock);
>>> + ret = -EEXIST;
>>> + goto fail;
>>> + }
>>> + TAILQ_INSERT_TAIL(&vdev_device_list, dev, next);
>>> + rte_spinlock_unlock(&vdev_device_list_lock);
>>> +
>>
>> I wonder if is possible to just leave the tailq locked until you
>> either insert the device into tailq, or figure out that it's not
>> possible? Seems like doing two locks here is unnecessary, unless
>> vdev_probe_all_drivers needs this tailq unlocked...
>
> My opinion is that we don't know what could be done in driver probe().
> It could possibly insert a new vdev (it does not happen now, but could
> happen in future?). So here, we call this with tailq unlocked. Or we
> keep it as simple as possible as you say?
I thought this code was responsible for inserting vdevs? I think it
would be generally bad design to insert vdev while inserting vdev :)
That said, it's a fair point, and i don't have a strong opinion on this,
so you can leave it as is if you want.
--
Thanks,
Anatoly
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