Re: [RFC PATCH net-next 2/4] switchdev: add fwd_mark generator helper

Jiri Pirko
2015-06-15T05:46:41Z

Sun, Jun 14, 2015 at 07:50:13PM CEST, sfeldma@gmail.com wrote:
>On Sat, Jun 13, 2015 at 11:56 PM, Jiri Pirko <jiri@resnulli.us> wrote:
>> Sat, Jun 13, 2015 at 08:04:28PM CEST, sfeldma@gmail.com wrote:
>>>From: Scott Feldman <sfeldma@gmail.com>
>>>
>>>skb->fwd_mark and dev->fwd_mark are 32-bit and should be unique for device
>>>and maybe even unique for a sub-set of ports within device, so add
>>>switchdev helper function to generate unique marks based on driver-supplied
>>>key. Typically, the driver would use device switch ID for key, and maybe
>>>additional fields in key for grouped ports such as bridge ifindex. The key
>>>can be of arbitrary length.
>>>
>>>The generator uses a global hash table to store fwd_marks hashed by key.
>>>
>>>Signed-off-by: Scott Feldman <sfeldma@gmail.com>
>
><snip>
>
>>>+u32 switchdev_mark_get(void *key, size_t key_len)
>>>+{
>>>+ struct switchdev_mark_ht_entry {
>>>+ struct hlist_node entry;
>>>+ void *key;
>>>+ size_t key_len;
>>>+ u32 key_crc32;
>>>+ u32 mark;
>>>+ } *entry;
>>>+ u32 key_crc32 = crc32(~0, key, key_len);
>>>+ u32 mark = 0;
>>>+ unsigned long flags;
>>>+
>>>+ spin_lock_irqsave(&switchdev_mark_lock, flags);
>>
>> I fail to see why _irqsave variant is needed here.
>
>I don't know what context caller is in, so using most conservative
>spinlock. Is there a better way?

I don't see why would someone call this from irq.