Re: [dpdk-dev] [PATCH] timer: fix resource leak in finalize

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 02-May-19 1:19 PM, Carrillo, Erik G wrote:
> 
> 
>> -----Original Message-----
>> From: Burakov, Anatoly
>> Sent: Thursday, May 2, 2019 4:18 AM
>> To: Carrillo, Erik G <erik.g.carrillo@intel.com>; rsanford@akamai.com;
>> thomas@monjalon.net
>> Cc: dev@dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH] timer: fix resource leak in finalize
>>
>> On 01-May-19 8:00 PM, Erik Gabriel Carrillo wrote:
>>> The finalize function should free the memzone created in the init
>>> function, rather than freeing the allocation the memzone references,
>>> otherwise a memzone descriptor can be leaked.
>>>
>>> Fixes: c0749f7096c7 ("timer: allow management in shared memory")
>>>
>>> Signed-off-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
>>> ---
>>>    lib/librte_timer/rte_timer.c | 12 ++++++++++--
>>>    1 file changed, 10 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/lib/librte_timer/rte_timer.c
>>> b/lib/librte_timer/rte_timer.c index eb46009..fb7a87e 100644
>>> --- a/lib/librte_timer/rte_timer.c
>>> +++ b/lib/librte_timer/rte_timer.c
>>> @@ -60,6 +60,7 @@ struct rte_timer_data {
>>>    };
>>>
>>>    #define RTE_MAX_DATA_ELS 64
>>> +static const struct rte_memzone *rte_timer_data_mz;
>>>    static struct rte_timer_data *rte_timer_data_arr;
>>>    static const uint32_t default_data_id;
>>>    static uint32_t rte_timer_subsystem_initialized; @@ -164,6 +165,7 @@
>>> rte_timer_subsystem_init_v1905(void)
>>>    		if (mz == NULL)
>>>    			return -EEXIST;
>>>
>>> +		rte_timer_data_mz = mz;
>>>    		rte_timer_data_arr = mz->addr;
>>>
>>>    		rte_timer_data_arr[default_data_id].internal_flags |= @@ -
>> 180,6
>>> +182,7 @@ rte_timer_subsystem_init_v1905(void)
>>>    	if (mz == NULL)
>>>    		return -ENOMEM;
>>>
>>> +	rte_timer_data_mz = mz;
>>>    	rte_timer_data_arr = mz->addr;
>>>
>>>    	for (i = 0; i < RTE_MAX_DATA_ELS; i++) { @@ -205,8 +208,13 @@
>>> BIND_DEFAULT_SYMBOL(rte_timer_subsystem_init, _v1905, 19.05);
>>>    void __rte_experimental
>>>    rte_timer_subsystem_finalize(void)
>>>    {
>>> -	if (rte_timer_data_arr)
>>> -		rte_free(rte_timer_data_arr);
>>> +	if (rte_eal_process_type() != RTE_PROC_PRIMARY)
>>> +		return;
>>> +
>>> +	if (!rte_timer_subsystem_initialized)
>>> +		return;
>>> +
>>> +	rte_memzone_free(rte_timer_data_mz);
>>
>> The patch is a correct fix, but the whole idea of this looks dangerous to me.
>>
>> If we exit the primary while secondaries are still running, wouldn't it basically
>> pull out timer data from under secondaries' feet?
>>
> 
> Ah yes - that’s right.  Perhaps it would be better to maintain a reference count of some sort such that the last process to exit could cause the memzone_free.
> 

It feels like a hack, to be honest. A process can crash or exit without 
calling rte_eal_cleanup(), which will lead to a memory leak due to 
refcount being stuck at a value that's not representing reality. It will 
be saf-er than current approach, but still not ideal.

However, i guess it's a good compromise, if i were to choose between a 
memory leak and a segfault :D I wonder if there is a better approach.

> Thanks,
> Erik
> 
>>>
>>>    	rte_timer_subsystem_initialized = 0;
>>>    }
>>>
>>
>>
>> --
>> Thanks,
>> Anatoly


-- 
Thanks,
Anatoly