Hi Anatoly,
thanks! The fact that memzone is found and matched only based on the name,
could it create potential problem like the one I described besides HW rings?
Kind regards,
Renata
________________________________
From: Burakov, Anatoly <anatoly.bura...@intel.com>
Sent: Tuesday, May 5, 2020 12:45 PM
To: Renata Saiakhova <renata.saiakh...@ekinops.com>; dev@dpdk.org <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 1/2] librte_ethdev: Introduce a function to
release HW rings
On 05-May-20 11:25 AM, Burakov, Anatoly wrote:
> On 03-May-20 5:26 PM, Renata Saiakhova wrote:
>> Free previously allocated memzone for HW rings
>>
>> Signed-off-by: Renata Saiakhova <renata.saiakh...@ekinops.com>
>> ---
>> lib/librte_ethdev/rte_ethdev.c | 23 +++++++++++++++++++++++
>> lib/librte_ethdev/rte_ethdev_driver.h | 14 ++++++++++++++
>> lib/librte_ethdev/rte_ethdev_version.map | 1 +
>> 3 files changed, 38 insertions(+)
>>
>> diff --git a/lib/librte_ethdev/rte_ethdev.c
>> b/lib/librte_ethdev/rte_ethdev.c
>> index 72aed59a5..c6d27e1aa 100644
>> --- a/lib/librte_ethdev/rte_ethdev.c
>> +++ b/lib/librte_ethdev/rte_ethdev.c
>> @@ -4206,6 +4206,29 @@ rte_eth_dma_zone_reserve(const struct
>> rte_eth_dev *dev, const char *ring_name,
>> RTE_MEMZONE_IOVA_CONTIG, align);
>> }
>> +int
>> +rte_eth_dma_zone_free(const struct rte_eth_dev *dev, const char
>> *ring_name,
>> + uint16_t queue_id)
>> +{
>> + char z_name[RTE_MEMZONE_NAMESIZE];
>> + const struct rte_memzone *mz;
>> + int rc = 0;
>> +
>> + snprintf(z_name, sizeof(z_name), "eth_p%d_q%d_%s",
>> + dev->data->port_id, queue_id, ring_name);
>> + if (rc >= RTE_MEMZONE_NAMESIZE) {
>> + RTE_ETHDEV_LOG(ERR, "ring name too long\n");
>> + rte_errno = ENAMETOOLONG;
>> + return NULL;
>> + }
>> +
>> + mz = rte_memzone_lookup(z_name);
>> + if (mz)
>> + rc = rte_memzone_free(mz);
>
> This is racy. Please just use rte_memzone_free() unconditionally. It'll
> return 0 if memzone existed, or will set rte_errno to EINVAL if it
> didn't. (this is suboptimal, it should be ENOENT, but changing this
> would be an API break... I'll submit a patch for future release to fix
> this)
>
My apologies, just using rte_memzone_free will not solve the problem
because you don't have memzone pointer. Now that i think of it, the
rte_eth_dma_zone_reserve() suffers from this issue too, and the problem
is lack of atomic "find or create" memzone API.
This patch is OK for now, as it follows similar code in
rte_eth_dma_zone_reserve(), but ideally, this should be fixed at the
memzone API level. I'll see if i can cobble together a quick patchset
adding atomic "find or reserve" and "find and free" operations.
--
Thanks,
Anatoly
