Ray Kinsella <m...@ashroe.eu> writes:
> Thomas Monjalon <tho...@monjalon.net> writes:
>
>> 14/02/2022 17:06, Ray Kinsella:
>>> Thomas Monjalon <tho...@monjalon.net> writes:
>>> > 14/02/2022 11:16, Ray Kinsella:
>>> >> Ray Kinsella <m...@ashroe.eu> writes:
>>> >> > Thomas Monjalon <tho...@monjalon.net> writes:
>>> >> >> 02/02/2022 12:44, Ray Kinsella:
>>> >> >>> Ferruh Yigit <ferruh.yi...@intel.com> writes:
>>> >> >>> > On 1/28/2022 12:48 PM, Kalesh A P wrote:
>>> >> >>> >> --- a/lib/ethdev/rte_ethdev.h
>>> >> >>> >> +++ b/lib/ethdev/rte_ethdev.h
>>> >> >>> >> @@ -3818,6 +3818,24 @@ enum rte_eth_event_type {
>>> >> >>> >> RTE_ETH_EVENT_DESTROY, /**< port is released */
>>> >> >>> >> RTE_ETH_EVENT_IPSEC, /**< IPsec offload related
>>> >> >>> >> event */
>>> >> >>> >> RTE_ETH_EVENT_FLOW_AGED,/**< New aged-out flows is
>>> >> >>> >> detected */
>>> >> >>> >> + RTE_ETH_EVENT_ERR_RECOVERING,
>>> >> >>> >> + /**< port recovering from an error
>>> >> >>> >> + *
>>> >> >>> >> + * PMD detected a FW reset or error condition.
>>> >> >>> >> + * PMD will try to recover from the error.
>>> >> >>> >> + * Data path may be quiesced and Control path
>>> >> >>> >> operations
>>> >> >>> >> + * may fail at this time.
>>> >> >>> >> + */
>>> >> >>> >> + RTE_ETH_EVENT_RECOVERED,
>>> >> >>> >> + /**< port recovered from an error
>>> >> >>> >> + *
>>> >> >>> >> + * PMD has recovered from the error condition.
>>> >> >>> >> + * Control path and Data path are up now.
>>> >> >>> >> + * PMD re-configures the port to the state
>>> >> >>> >> prior to the error.
>>> >> >>> >> + * Since the device has undergone a reset, flow
>>> >> >>> >> rules
>>> >> >>> >> + * offloaded prior to reset may be lost and
>>> >> >>> >> + * the application should recreate the rules
>>> >> >>> >> again.
>>> >> >>> >> + */
>>> >> >>> >> RTE_ETH_EVENT_MAX /**< max value of this enum */
>>> >> >>> >
>>> >> >>> >
>>> >> >>> > Also ABI check complains about 'RTE_ETH_EVENT_MAX' value check,
>>> >> >>> > cc'ed more people
>>> >> >>> > to evaluate if it is a false positive:
>>> >> >>> >
>>> >> >>> >
>>> >> >>> > 1 function with some indirect sub-type change:
>>> >> >>> > [C] 'function int rte_eth_dev_callback_register(uint16_t,
>>> >> >>> > rte_eth_event_type, rte_eth_dev_cb_fn, void*)' at
>>> >> >>> > rte_ethdev.c:4637:1 has some indirect sub-type changes:
>>> >> >>> > parameter 3 of type 'typedef rte_eth_dev_cb_fn' has sub-type
>>> >> >>> > changes:
>>> >> >>> > underlying type 'int (typedef uint16_t, enum
>>> >> >>> > rte_eth_event_type, void*, void*)*' changed:
>>> >> >>> > in pointed to type 'function type int (typedef uint16_t,
>>> >> >>> > enum rte_eth_event_type, void*, void*)':
>>> >> >>> > parameter 2 of type 'enum rte_eth_event_type' has
>>> >> >>> > sub-type changes:
>>> >> >>> > type size hasn't changed
>>> >> >>> > 2 enumerator insertions:
>>> >> >>> > 'rte_eth_event_type::RTE_ETH_EVENT_ERR_RECOVERING'
>>> >> >>> > value '11'
>>> >> >>> > 'rte_eth_event_type::RTE_ETH_EVENT_RECOVERED' value
>>> >> >>> > '12'
>>> >> >>> > 1 enumerator change:
>>> >> >>> > 'rte_eth_event_type::RTE_ETH_EVENT_MAX' from value
>>> >> >>> > '11' to '13' at rte_ethdev.h:3807:1
>>> >> >>>
>>> >> >>> I don't immediately see the problem that this would cause.
>>> >> >>> There are no array sizes etc dependent on the value of MAX for
>>> >> >>> instance.
>>> >> >>>
>>> >> >>> Looks safe?
>>> >> >>
>>> >> >> We never know how this enum will be used by the application.
>>> >> >> The max value may be used for the size of an event array.
>>> >> >> It looks a real ABI issue unfortunately.
>>> >> >
>>> >> > Right - but we only really care about it when an array size based on
>>> >> > MAX
>>> >> > is likely to be passed to DPDK, which doesn't apply in this case.
>>> >
>>> > I don't completely agree.
>>> > A developer may assume an event will never exceed MAX value.
>>> > However, after an upgrade of DPDK without app rebuild,
>>> > a higher event value may be received in the app,
>>> > breaking the assumption.
>>> > Should we consider this case as an ABI breakage?
>>>
>>> Nope - I think we should explicitly exclude MAX values from any
>>> ABI guarantee, as being able to change them is key to our be able to
>>> evolve DPDK while maintaining ABI stability.
>>
>> Or we can simply remove the MAX values so there is no confusion.
>>
>>> Consider what it means applying the ABI policy to a MAX value, you are
>>> in effect saying that that no value can be added to this enumeration
>>> until the next ABI version, for me this is very restrictive without a
>>> solid reason.
>>
>> I agree it is too much restrictive, that's why I am advocating
>> for their removal.
>
> I think that would be simplest yes - may require some rework of the
> sample code though. I will take a look at it.
Thinking about this some more - we can't remove the MAX values between
now the next stable ABI. So we may need a short term plan, and long term
plan.
Long term, I agree we look at every _MAX enumeration value and ask do we
need it.
Short term (until the next ABI), we still need to answer the question do
we allow people to change _MAX values?
>>
>>> >> > I noted that some Linux folks explicitly mark similar MAX values as not
>>> >> > part of the ABI.
>>> >> >
>>> >> > /usr/include/linux/perf_event.h
>>> >> > 37: PERF_TYPE_MAX, /* non-ABI */
>>> >> > 60: PERF_COUNT_HW_MAX, /* non-ABI */
>>> >> > 79: PERF_COUNT_HW_CACHE_MAX, /* non-ABI */
>>> >> > 87: PERF_COUNT_HW_CACHE_OP_MAX, /* non-ABI */
>>> >> > 94: PERF_COUNT_HW_CACHE_RESULT_MAX, /* non-ABI */
>>> >> > 116: PERF_COUNT_SW_MAX, /* non-ABI */
>>> >> > 149: PERF_SAMPLE_MAX = 1U << 24, /* non-ABI */
>>> >> > 151: __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, /*
>>> >> > non-ABI; internal use */
>>> >> > 189: PERF_SAMPLE_BRANCH_MAX_SHIFT /* non-ABI */
>>> >> > 267: PERF_TXN_MAX = (1 << 8), /* non-ABI */
>>> >> > 301: PERF_FORMAT_MAX = 1U << 4, /* non-ABI */
>>> >> > 1067: PERF_RECORD_MAX, /* non-ABI */
>>> >> > 1078: PERF_RECORD_KSYMBOL_TYPE_MAX /* non-ABI */
>>> >> > 1087: PERF_BPF_EVENT_MAX, /* non-ABI */
>>> >>
>>> >> Any thoughts on similarly annotating all our _MAX enums in the same way?
>>> >> We could also add a section in the ABI Policy to make it explicit _MAX
>>> >> enum values are not part of the ABI - what do folks think?
>>> >
>>> > Interesting. I am not sure it is always ABI-safe though.
--
Regards, Ray K
