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.
>
>> >> > 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
