[1/2] baseband/fpga_5gnr_fec: use new barrier API

Message ID 20240222162113.1896370-1-maxime.coquelin@redhat.com (mailing list archive)
State Deferred
Delegated to: Maxime Coquelin
Headers
Series [1/2] baseband/fpga_5gnr_fec: use new barrier API |

Checks

Context Check Description
ci/checkpatch success coding style OK

Commit Message

Maxime Coquelin Feb. 22, 2024, 4:21 p.m. UTC
  rte_smp_rmb() is deprecated, use the new API instead as
suggested in rte_atomic header.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
  

Comments

Chautru, Nicolas Feb. 22, 2024, 6:05 p.m. UTC | #1
Hi Maxime, 

Why would we change this here and now? Is the intent not to use new suggested semantics for new patches only?
Are all DPDK drivers being changed?
I am unsure we would want to change these drivers, this is kind of risk introduced by code churn that gets ecosystem unwilling to move to latest version.
These memory barriers issues are awful to troubleshoot or properly validate, so personally quite reluctant to change. 

Thanks
Nic

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Thursday, February 22, 2024 8:21 AM
> To: dev@dpdk.org; Chautru, Nicolas <nicolas.chautru@intel.com>; Vargas,
> Hernan <hernan.vargas@intel.com>; Marchand, David
> <david.marchand@redhat.com>; thomas@monjalon.net;
> roretzla@linux.microsoft.com
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> Subject: [PATCH 1/2] baseband/fpga_5gnr_fec: use new barrier API
> 
> rte_smp_rmb() is deprecated, use the new API instead as suggested in
> rte_atomic header.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
> b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
> index efc1d3a772..314c87350e 100644
> --- a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
> +++ b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
> @@ -2661,7 +2661,7 @@ vc_5gnr_dequeue_ldpc_enc_one_op_cb(struct
> fpga_5gnr_queue *q, struct rte_bbdev_e
>  		return -1;
> 
>  	/* make sure the response is read atomically */
> -	rte_smp_rmb();
> +	rte_atomic_thread_fence(rte_memory_order_acquire);
> 
>  	rte_bbdev_log_debug("DMA response desc %p", desc);
> 
> @@ -2690,7 +2690,7 @@ agx100_dequeue_ldpc_enc_one_op_cb(struct
> fpga_5gnr_queue *q, struct rte_bbdev_en
>  		return -1;
> 
>  	/* make sure the response is read atomically. */
> -	rte_smp_rmb();
> +	rte_atomic_thread_fence(rte_memory_order_acquire);
> 
>  	rte_bbdev_log_debug("DMA response desc %p", desc);
> 
> @@ -2722,7 +2722,7 @@ vc_5gnr_dequeue_ldpc_dec_one_op_cb(struct
> fpga_5gnr_queue *q, struct rte_bbdev_d
>  		return -1;
> 
>  	/* make sure the response is read atomically */
> -	rte_smp_rmb();
> +	rte_atomic_thread_fence(rte_memory_order_acquire);
> 
>  #ifdef RTE_LIBRTE_BBDEV_DEBUG
>  	vc_5gnr_print_dma_dec_desc_debug_info(desc);
> @@ -2768,7 +2768,7 @@ agx100_dequeue_ldpc_dec_one_op_cb(struct
> fpga_5gnr_queue *q, struct rte_bbdev_de
>  		return -1;
> 
>  	/* make sure the response is read atomically. */
> -	rte_smp_rmb();
> +	rte_atomic_thread_fence(rte_memory_order_acquire);
> 
>  #ifdef RTE_LIBRTE_BBDEV_DEBUG
>  	agx100_print_dma_dec_desc_debug_info(desc);
> --
> 2.43.0
  
Maxime Coquelin Feb. 26, 2024, 11:03 a.m. UTC | #2
Hello,

On 2/22/24 19:05, Chautru, Nicolas wrote:
> Hi Maxime,
> 
> Why would we change this here and now? Is the intent not to use new suggested semantics for new patches only?

The pull request was rejected because of the use of such barrier, which 
is reported by checkpatch.

### [PATCH] baseband/fpga_5gnr_fec: add AGX100 support
Warning in drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c:
Using rte_smp_[r/w]mb

> Are all DPDK drivers being changed?

My understanding is that for now, only new occurrences are prohibited,
can you confirm Tyler?

If so we could only change for now the patch adding ACX100.
But... I preferred doing the changes for all bbdev drivers for
consistency.

> I am unsure we would want to change these drivers, this is kind of risk introduced by code churn that gets ecosystem unwilling to move to latest version.

I think it is better to change now that we are far from the next LTS.

> These memory barriers issues are awful to troubleshoot or properly validate, so personally quite reluctant to change.

If I disassemble fpga_dequeue_enc() with and without the patch, I cannot
spot a difference.

Thomas, are you waiting for this series to be applied to take the pull
request that was initially for -rc1?

Thanks,
Maxime

> Thanks
> Nic
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Thursday, February 22, 2024 8:21 AM
>> To: dev@dpdk.org; Chautru, Nicolas <nicolas.chautru@intel.com>; Vargas,
>> Hernan <hernan.vargas@intel.com>; Marchand, David
>> <david.marchand@redhat.com>; thomas@monjalon.net;
>> roretzla@linux.microsoft.com
>> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Subject: [PATCH 1/2] baseband/fpga_5gnr_fec: use new barrier API
>>
>> rte_smp_rmb() is deprecated, use the new API instead as suggested in
>> rte_atomic header.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>>   drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>> b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>> index efc1d3a772..314c87350e 100644
>> --- a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>> +++ b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>> @@ -2661,7 +2661,7 @@ vc_5gnr_dequeue_ldpc_enc_one_op_cb(struct
>> fpga_5gnr_queue *q, struct rte_bbdev_e
>>   		return -1;
>>
>>   	/* make sure the response is read atomically */
>> -	rte_smp_rmb();
>> +	rte_atomic_thread_fence(rte_memory_order_acquire);
>>
>>   	rte_bbdev_log_debug("DMA response desc %p", desc);
>>
>> @@ -2690,7 +2690,7 @@ agx100_dequeue_ldpc_enc_one_op_cb(struct
>> fpga_5gnr_queue *q, struct rte_bbdev_en
>>   		return -1;
>>
>>   	/* make sure the response is read atomically. */
>> -	rte_smp_rmb();
>> +	rte_atomic_thread_fence(rte_memory_order_acquire);
>>
>>   	rte_bbdev_log_debug("DMA response desc %p", desc);
>>
>> @@ -2722,7 +2722,7 @@ vc_5gnr_dequeue_ldpc_dec_one_op_cb(struct
>> fpga_5gnr_queue *q, struct rte_bbdev_d
>>   		return -1;
>>
>>   	/* make sure the response is read atomically */
>> -	rte_smp_rmb();
>> +	rte_atomic_thread_fence(rte_memory_order_acquire);
>>
>>   #ifdef RTE_LIBRTE_BBDEV_DEBUG
>>   	vc_5gnr_print_dma_dec_desc_debug_info(desc);
>> @@ -2768,7 +2768,7 @@ agx100_dequeue_ldpc_dec_one_op_cb(struct
>> fpga_5gnr_queue *q, struct rte_bbdev_de
>>   		return -1;
>>
>>   	/* make sure the response is read atomically. */
>> -	rte_smp_rmb();
>> +	rte_atomic_thread_fence(rte_memory_order_acquire);
>>
>>   #ifdef RTE_LIBRTE_BBDEV_DEBUG
>>   	agx100_print_dma_dec_desc_debug_info(desc);
>> --
>> 2.43.0
>
  
Maxime Coquelin Feb. 27, 2024, 4:56 p.m. UTC | #3
Hi Tyler,

On 2/26/24 12:03, Maxime Coquelin wrote:
> Hello,
> 
> On 2/22/24 19:05, Chautru, Nicolas wrote:
>> Hi Maxime,
>>
>> Why would we change this here and now? Is the intent not to use new 
>> suggested semantics for new patches only?
> 
> The pull request was rejected because of the use of such barrier, which 
> is reported by checkpatch.
> 
> ### [PATCH] baseband/fpga_5gnr_fec: add AGX100 support
> Warning in drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c:
> Using rte_smp_[r/w]mb
> 
>> Are all DPDK drivers being changed?
> 
> My understanding is that for now, only new occurrences are prohibited,
> can you confirm Tyler?

Could you please clarify whether conversion for existing rte_smp_rmb()
calls to rte_atomic_thread_fence() in drivers is planned, or only new
occurrences are prohibited?

Thanks in advances,
Maxime

> If so we could only change for now the patch adding ACX100.
> But... I preferred doing the changes for all bbdev drivers for
> consistency.
> 
>> I am unsure we would want to change these drivers, this is kind of 
>> risk introduced by code churn that gets ecosystem unwilling to move to 
>> latest version.
> 
> I think it is better to change now that we are far from the next LTS.
> 
>> These memory barriers issues are awful to troubleshoot or properly 
>> validate, so personally quite reluctant to change.
> 
> If I disassemble fpga_dequeue_enc() with and without the patch, I cannot
> spot a difference.
> 
> Thomas, are you waiting for this series to be applied to take the pull
> request that was initially for -rc1?
> 
> Thanks,
> Maxime
> 
>> Thanks
>> Nic
>>
>>> -----Original Message-----
>>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>>> Sent: Thursday, February 22, 2024 8:21 AM
>>> To: dev@dpdk.org; Chautru, Nicolas <nicolas.chautru@intel.com>; Vargas,
>>> Hernan <hernan.vargas@intel.com>; Marchand, David
>>> <david.marchand@redhat.com>; thomas@monjalon.net;
>>> roretzla@linux.microsoft.com
>>> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
>>> Subject: [PATCH 1/2] baseband/fpga_5gnr_fec: use new barrier API
>>>
>>> rte_smp_rmb() is deprecated, use the new API instead as suggested in
>>> rte_atomic header.
>>>
>>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>>> ---
>>>   drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c | 8 ++++----
>>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>>> b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>>> index efc1d3a772..314c87350e 100644
>>> --- a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>>> +++ b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
>>> @@ -2661,7 +2661,7 @@ vc_5gnr_dequeue_ldpc_enc_one_op_cb(struct
>>> fpga_5gnr_queue *q, struct rte_bbdev_e
>>>           return -1;
>>>
>>>       /* make sure the response is read atomically */
>>> -    rte_smp_rmb();
>>> +    rte_atomic_thread_fence(rte_memory_order_acquire);
>>>
>>>       rte_bbdev_log_debug("DMA response desc %p", desc);
>>>
>>> @@ -2690,7 +2690,7 @@ agx100_dequeue_ldpc_enc_one_op_cb(struct
>>> fpga_5gnr_queue *q, struct rte_bbdev_en
>>>           return -1;
>>>
>>>       /* make sure the response is read atomically. */
>>> -    rte_smp_rmb();
>>> +    rte_atomic_thread_fence(rte_memory_order_acquire);
>>>
>>>       rte_bbdev_log_debug("DMA response desc %p", desc);
>>>
>>> @@ -2722,7 +2722,7 @@ vc_5gnr_dequeue_ldpc_dec_one_op_cb(struct
>>> fpga_5gnr_queue *q, struct rte_bbdev_d
>>>           return -1;
>>>
>>>       /* make sure the response is read atomically */
>>> -    rte_smp_rmb();
>>> +    rte_atomic_thread_fence(rte_memory_order_acquire);
>>>
>>>   #ifdef RTE_LIBRTE_BBDEV_DEBUG
>>>       vc_5gnr_print_dma_dec_desc_debug_info(desc);
>>> @@ -2768,7 +2768,7 @@ agx100_dequeue_ldpc_dec_one_op_cb(struct
>>> fpga_5gnr_queue *q, struct rte_bbdev_de
>>>           return -1;
>>>
>>>       /* make sure the response is read atomically. */
>>> -    rte_smp_rmb();
>>> +    rte_atomic_thread_fence(rte_memory_order_acquire);
>>>
>>>   #ifdef RTE_LIBRTE_BBDEV_DEBUG
>>>       agx100_print_dma_dec_desc_debug_info(desc);
>>> -- 
>>> 2.43.0
>>
  

Patch

diff --git a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
index efc1d3a772..314c87350e 100644
--- a/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
+++ b/drivers/baseband/fpga_5gnr_fec/rte_fpga_5gnr_fec.c
@@ -2661,7 +2661,7 @@  vc_5gnr_dequeue_ldpc_enc_one_op_cb(struct fpga_5gnr_queue *q, struct rte_bbdev_e
 		return -1;
 
 	/* make sure the response is read atomically */
-	rte_smp_rmb();
+	rte_atomic_thread_fence(rte_memory_order_acquire);
 
 	rte_bbdev_log_debug("DMA response desc %p", desc);
 
@@ -2690,7 +2690,7 @@  agx100_dequeue_ldpc_enc_one_op_cb(struct fpga_5gnr_queue *q, struct rte_bbdev_en
 		return -1;
 
 	/* make sure the response is read atomically. */
-	rte_smp_rmb();
+	rte_atomic_thread_fence(rte_memory_order_acquire);
 
 	rte_bbdev_log_debug("DMA response desc %p", desc);
 
@@ -2722,7 +2722,7 @@  vc_5gnr_dequeue_ldpc_dec_one_op_cb(struct fpga_5gnr_queue *q, struct rte_bbdev_d
 		return -1;
 
 	/* make sure the response is read atomically */
-	rte_smp_rmb();
+	rte_atomic_thread_fence(rte_memory_order_acquire);
 
 #ifdef RTE_LIBRTE_BBDEV_DEBUG
 	vc_5gnr_print_dma_dec_desc_debug_info(desc);
@@ -2768,7 +2768,7 @@  agx100_dequeue_ldpc_dec_one_op_cb(struct fpga_5gnr_queue *q, struct rte_bbdev_de
 		return -1;
 
 	/* make sure the response is read atomically. */
-	rte_smp_rmb();
+	rte_atomic_thread_fence(rte_memory_order_acquire);
 
 #ifdef RTE_LIBRTE_BBDEV_DEBUG
 	agx100_print_dma_dec_desc_debug_info(desc);