On 29/05/2013 23:09, Ben Hutchings wrote:
> On Wed, 2013-05-29 at 09:39 +0300, Eliezer Tamir wrote:
>> +void napi_hash_add(struct napi_struct *napi)
>> +{
>> + if (!test_and_set_bit(NAPI_STATE_HASHED, &napi->state)) {
>> +
>> + spin_lock(&napi_hash_lock);
>> +
>> + /* 0 is not a valid id */
>> + napi->napi_id = 0;
>> + while (!napi->napi_id)
>> + napi->napi_id = ++napi_gen_id;
>
> Suppose we're loading/unloading one driver repeatedly while another one
> remains loaded the whole time. Then once napi_gen_id wraps around, the
> same ID can be assigned to multiple contexts.
>
> So far as I can see, assigning the same ID twice will just make polling
> stop working for one of the NAPI contexts; I don't think it causes a
> crash. And it is exceedingly unlikely to happen in production. But if
> you're going to the trouble of handling wrap-around at all, you'd better
> handle this.
OK
> [...]
>> +/* must be called under rcu_read_lock(), as we dont take a reference */
>> +struct napi_struct *napi_by_id(int napi_id)
>> +{
>> + unsigned int hash = napi_id % HASH_SIZE(napi_hash);
> [...]
>
> napi_id should be declared unsigned int here, as elsewhere. The
> division can't actually yield a negative result because HASH_SIZE() has
> type size_t and napi_id is promoted to match, but I had to go and look
> at hashtable.h to check that.
Good catch,
Thanks,
Eliezer
------------------------------------------------------------------------------
Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET
Get 100% visibility into your production application - at no cost.
Code-level diagnostics for performance bottlenecks with <2% overhead
Download for free and get started troubleshooting in minutes.
http://p.sf.net/sfu/appdyn_d2d_ap1
_______________________________________________
E1000-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/e1000-devel
To learn more about Intel® Ethernet, visit
http://communities.intel.com/community/wired
