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SubjectRe: [PATCH 1/1] net: Add rtnl_lock for netif_device_attach/detach
The comment is trying to explain why add a lock here.

On 04/19/2014 03:01 AM, Sergei Shtylyov wrote:
> Hello.
>
> On 04/16/2014 11:08 AM, Li, Zhen-Hua wrote:
>
>> From: "Li, Zhen-Hua" <zhen-hual@hp.com>
>
>> As netif_running is called in netif_device_attach/detach. There
>> should be
>> rtnl_lock/unlock called, to avoid dev stat change during
>> netif_device_attach
>> and detach being called.
>> I checked NIC some drivers, some of them have
>> netif_device_attach/detach
>> called between rtnl_lock/unlock, while some drivers do not.
>
>> This patch is tring to find a generic way to fix this for all NIC
>> drivers.
>
>> Signed-off-by: Li, Zhen-Hua <zhen-hual@hp.com>
>> ---
>> net/core/dev.c | 18 ++++++++++++++++++
>> 1 file changed, 18 insertions(+)
>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 5b3042e..795bbc5 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -2190,10 +2190,19 @@ EXPORT_SYMBOL(__dev_kfree_skb_any);
>> */
>> void netif_device_detach(struct net_device *dev)
>> {
>> + /**
>
> Hm, why kernel-doc style comment here?
>
>> + * As netif_running is called , rtnl_lock and unlock are needed to
>> + * avoid __LINK_STATE_START bit changes during this function call.
>> + */
>> + int need_unlock;
>> +
>> + need_unlock = rtnl_trylock();
>> if (test_and_clear_bit(__LINK_STATE_PRESENT, &dev->state) &&
>> netif_running(dev)) {
>> netif_tx_stop_all_queues(dev);
>> }
>> + if (need_unlock)
>> + rtnl_unlock();
>> }
>> EXPORT_SYMBOL(netif_device_detach);
>>
>> @@ -2205,11 +2214,20 @@ EXPORT_SYMBOL(netif_device_detach);
>> */
>> void netif_device_attach(struct net_device *dev)
>> {
>> + /**
>
> ... and here?
>
>> + * As netif_running is called , rtnl_lock and unlock are needed to
>> + * avoid __LINK_STATE_START bit changes during this function call.
>> + */
>
> WBR, Sergei
>



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