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From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: "Carrillo, Erik G" <erik.g.carrillo@intel.com>,
	"rsanford@akamai.com" <rsanford@akamai.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2] timer: fix resource leak in finalize
Date: Wed, 8 May 2019 09:49:58 +0100	[thread overview]
Message-ID: <efc5b7ac-1b13-f219-9bd7-8f8805450e43@intel.com> (raw)
Message-ID: <20190508084958.Ts0xxYRoyBat4APWVPx9PUxUCUCzuGuwFGt77u1DxD4@z> (raw)
In-Reply-To: <BE54F058557D9A4FAC1D84E2FC6D875723405E77@fmsmsx115.amr.corp.intel.com>

On 07-May-19 11:04 PM, Carrillo, Erik G wrote:
> Hi Anatoly,
> 
> Thanks for the review.  Comments in-line:
> 
> <...snipped...>
> 
>>>    #define RTE_MAX_DATA_ELS 64
>>> +static const struct rte_memzone *rte_timer_data_mz; static
>>> +rte_atomic16_t *rte_timer_mz_refcnt;
>>>    static struct rte_timer_data *rte_timer_data_arr;
>>>    static const uint32_t default_data_id;
>>>    static uint32_t rte_timer_subsystem_initialized; @@ -155,6 +157,7 @@
>>> rte_timer_subsystem_init_v1905(void)
>>>    	struct rte_timer_data *data;
>>>    	int i, lcore_id;
>>>    	static const char *mz_name = "rte_timer_mz";
>>> +	size_t data_arr_size = RTE_MAX_DATA_ELS *
>>> +sizeof(*rte_timer_data_arr);
>>
>> nitpicking, but... const?
>>
> 
> No problem - I'll make this change if this line persists into the next version.
> 
> <...snipped...>
> 
>>>
>>> @@ -205,8 +216,11 @@
>> 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_timer_subsystem_initialized)
>>> +		return;
>>> +
>>> +	if (rte_atomic16_dec_and_test(rte_timer_mz_refcnt))
>>> +		rte_memzone_free(rte_timer_data_mz);
>>
>> I think there's a race here. You may get preempted after test but before
>> free, where another secondary could initialize. As far as i know, we also
> 
> Indeed, thanks for catching this.
> 
>> support a case when secondary initializes after primary stops running.
>>
>> Let's even suppose that we allow secondary processes to initialize the timer
>> subsystem by reserving memzone and checking rte_errno. You would still
>> have a chance of two init/deinit conflicting, because there's a hole between
>> memzone allocation and atomic increment.
>>
>> I don't think this race can be resolved in a safe way, so we might just have to
>> settle for a memory leak.
>>
> 
> I don't see a solution here currently either.  I'll look at removing the memzone_free()
> call and possibly the rte_timer_subsystem_finalize() API, since it seems like
> there's no reason for it to exist if it can't free the allocations.

I wonder if there are other places in DPDK where this pattern is used.

Technically, this kind of thing /could/ be resolved by having something 
in our multiprocess shared memory outside of DPDK heap. I.e. store 
something in rte_eal_memconfig like some other things do. This change, 
however, would require an ABI break, so while changing this particular 
API won't need a deprecation notice, the change itself would.

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


-- 
Thanks,
Anatoly

  parent reply	other threads:[~2019-05-08  8:50 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-01 19:00 [dpdk-dev] [PATCH] " Erik Gabriel Carrillo
2019-05-01 19:00 ` Erik Gabriel Carrillo
2019-05-02  9:18 ` Burakov, Anatoly
2019-05-02  9:18   ` Burakov, Anatoly
2019-05-02 12:19   ` Carrillo, Erik G
2019-05-02 12:19     ` Carrillo, Erik G
2019-05-02 13:03     ` Burakov, Anatoly
2019-05-02 13:03       ` Burakov, Anatoly
2019-05-02 13:48       ` Carrillo, Erik G
2019-05-02 13:48         ` Carrillo, Erik G
2019-05-03 22:54 ` [dpdk-dev] [PATCH v2] " Erik Gabriel Carrillo
2019-05-03 22:54   ` Erik Gabriel Carrillo
2019-05-07 11:03   ` Burakov, Anatoly
2019-05-07 11:03     ` Burakov, Anatoly
2019-05-07 22:04     ` Carrillo, Erik G
2019-05-07 22:04       ` Carrillo, Erik G
2019-05-08  8:49       ` Burakov, Anatoly [this message]
2019-05-08  8:49         ` Burakov, Anatoly
2019-05-08 23:01         ` Carrillo, Erik G
2019-05-08 23:01           ` Carrillo, Erik G
2019-05-09  7:44           ` Thomas Monjalon
2019-05-09  7:44             ` Thomas Monjalon
2019-05-08 22:35   ` [dpdk-dev] [PATCH v3] " Erik Gabriel Carrillo
2019-05-08 22:35     ` Erik Gabriel Carrillo
2019-05-09  8:29     ` Burakov, Anatoly
2019-05-09  8:29       ` Burakov, Anatoly
2019-06-05  9:33       ` Thomas Monjalon
2019-06-05  9:47         ` Burakov, Anatoly
2019-06-25 16:11     ` [dpdk-dev] [PATCH 0/2] Fix timer resource leak Anatoly Burakov
2019-07-05 13:20       ` [dpdk-dev] [PATCH v2 0/1] " Anatoly Burakov
2019-07-05 17:22         ` [dpdk-dev] [PATCH v3 " Anatoly Burakov
2019-07-05 17:22         ` [dpdk-dev] [PATCH v3 1/1] timer: fix resource leak in finalize Anatoly Burakov
2019-07-05 22:06           ` Thomas Monjalon
2019-07-05 13:20       ` [dpdk-dev] [PATCH v2 " Anatoly Burakov
2019-06-25 16:11     ` [dpdk-dev] [PATCH 1/2] eal: add internal locks for timer lib into EAL Anatoly Burakov
2019-06-27 18:41       ` Carrillo, Erik G
2019-07-04  9:09       ` David Marchand
2019-07-04 10:44         ` Burakov, Anatoly
2019-06-25 16:11     ` [dpdk-dev] [PATCH 2/2] timer: fix resource leak in finalize Anatoly Burakov
2019-06-27 18:48       ` Carrillo, Erik G
2019-07-04  9:10       ` David Marchand
2019-07-04 10:45         ` Burakov, Anatoly
2019-07-04 10:50           ` David Marchand

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