Re: [dpdk-dev] [PATCH] eal: fix lcore state bug

[Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>]

Hi David,

The patch is here for quite a while and I believe it's assign to you.
Today there were some questions about it on 
https://bugs.dpdk.org/show_bug.cgi?id=464

Is there anything else to be done, so it can be accepted?

Best regards
Lukasz

W dniu 28.04.2020 o 03:21, Lukasz Wojciechowski pisze:
> The rte_service_lcore_reset_all function stops execution of services
> on all lcores and switches them back from ROLE_SERVICE to ROLE_RTE.
> However the thread loop for slave lcores (eal_thread_loop) distincts these
> roles to set lcore state after processing delegated function.
> It sets WAIT state for ROLE_SERVICE, but FINISHED for ROLE_RTE.
> So changing the role to RTE before stopping work in slave lcores
> causes lcores to end in FINISHED state. That is why the rte_eal_lcore_wait
> must be run after rte_service_lcore_reset_all to bring back lcores to
> launchable (WAIT) state.
> This has been fixed in test app and clarified in API documentation.
>
> Setting the state to WAIT in rte_service_runner_func is premature
> as the rte_service_runner_func function is still a part of the lcore
> function delegated to slave lcore. The state is overwritten anyway in
> slave lcore thread loop. This premature setting state to WAIT might
> however cause rte_eal_lcore_wait, that was called by the application,
> to return before slave lcore thread set the FINISHED state. That's
> why it is removed from librte_eal rte_service_runner_func function.
>
> Bugzilla ID: 464
> Fixes: 21698354c832 ("service: introduce service cores concept")
> Fixes: f038a81e1c56 ("service: add unit tests")
> Cc: harry.van.haaren@intel.com
> Cc: stable@dpdk.org
>
> Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
> ---
>   app/test/test_service_cores.c        | 1 +
>   lib/librte_eal/common/rte_service.c  | 2 --
>   lib/librte_eal/include/rte_service.h | 4 ++++
>   3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/app/test/test_service_cores.c b/app/test/test_service_cores.c
> index a922c7ddc..2a4978e29 100644
> --- a/app/test/test_service_cores.c
> +++ b/app/test/test_service_cores.c
> @@ -114,6 +114,7 @@ unregister_all(void)
>   	}
>   
>   	rte_service_lcore_reset_all();
> +	rte_eal_mp_wait_lcore();
>   
>   	return TEST_SUCCESS;
>   }
> diff --git a/lib/librte_eal/common/rte_service.c b/lib/librte_eal/common/rte_service.c
> index 70d17a5d7..018876199 100644
> --- a/lib/librte_eal/common/rte_service.c
> +++ b/lib/librte_eal/common/rte_service.c
> @@ -458,8 +458,6 @@ rte_service_runner_func(void *arg)
>   		rte_smp_rmb();
>   	}
>   
> -	lcore_config[lcore].state = WAIT;
> -
>   	return 0;
>   }
>   
> diff --git a/lib/librte_eal/include/rte_service.h b/lib/librte_eal/include/rte_service.h
> index d8701dd4c..acdda8c54 100644
> --- a/lib/librte_eal/include/rte_service.h
> +++ b/lib/librte_eal/include/rte_service.h
> @@ -300,6 +300,10 @@ int32_t rte_service_lcore_count(void);
>    * from duty, just unmaps all services / cores, and stops() the service cores.
>    * The runstate of services is not modified.
>    *
> + * The cores that are stopped with this call, are in FINISHED state and
> + * the application must take care of bringing them back to a launchable state:
> + * e.g. call *rte_eal_lcore_wait* on the lcore_id.
> + *
>    * @retval 0 Success
>    */
>   int32_t rte_service_lcore_reset_all(void);

-- 

Lukasz Wojciechowski
Principal Software Engineer

Samsung R&D Institute Poland
Samsung Electronics
Office +48 22 377 88 25
l.wojciechow@partner.samsung.com