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

["Carrillo, Erik G" <erik.g.carrillo@intel.com>]

> -----Original Message-----
> From: Burakov, Anatoly
> Sent: Thursday, May 2, 2019 8:04 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 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.

Ok, I will take a look at that approach then as a first step, since a process can already crash before calling rte_eal_cleanup(), which would result in leaks anyway.

Thanks,
Erik

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