[5/7] eal: register non-EAL threads as lcore

  DPDK allows calling some part of its API from a non-EAL thread but this
has some limitations.
OVS (and other applications) has its own thread management but still
want to avoid such limitations by hacking RTE_PER_LCORE(_lcore_id) and
faking EAL threads potentially unknown of some DPDK component.

Introduce a new API to register non-EAL thread and associate them to a
free lcore with a new EXTERNAL role.
This role denotes lcores that do not run DPDK mainloop and as such
prevents use of rte_eal_wait_lcore() and consorts.

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
 doc/guides/howto/debug_troubleshoot.rst   |  5 ++-
 lib/librte_eal/common/eal_common_lcore.c  | 44 +++++++++++++++++--
 lib/librte_eal/common/eal_common_thread.c | 45 ++++++++++++++++++++
 lib/librte_eal/common/eal_private.h       | 17 ++++++++
 lib/librte_eal/include/rte_eal.h          |  9 ----
 lib/librte_eal/include/rte_lcore.h        | 52 +++++++++++++++++------
 lib/librte_eal/rte_eal_version.map        |  4 ++
 7 files changed, 147 insertions(+), 29 deletions(-)
  

On 10/06/2020 15:45, David Marchand wrote:
> DPDK allows calling some part of its API from a non-EAL thread but this
> has some limitations.
> OVS (and other applications) has its own thread management but still
> want to avoid such limitations by hacking RTE_PER_LCORE(_lcore_id) and
> faking EAL threads potentially unknown of some DPDK component.
>
> Introduce a new API to register non-EAL thread and associate them to a
> free lcore with a new EXTERNAL role.
> This role denotes lcores that do not run DPDK mainloop and as such
> prevents use of rte_eal_wait_lcore() and consorts.
>
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>  doc/guides/howto/debug_troubleshoot.rst   |  5 ++-
>  lib/librte_eal/common/eal_common_lcore.c  | 44 +++++++++++++++++--
>  lib/librte_eal/common/eal_common_thread.c | 45 ++++++++++++++++++++
>  lib/librte_eal/common/eal_private.h       | 17 ++++++++
>  lib/librte_eal/include/rte_eal.h          |  9 ----
>  lib/librte_eal/include/rte_lcore.h        | 52 +++++++++++++++++------
>  lib/librte_eal/rte_eal_version.map        |  4 ++
>  7 files changed, 147 insertions(+), 29 deletions(-)
>
> diff --git a/doc/guides/howto/debug_troubleshoot.rst b/doc/guides/howto/debug_troubleshoot.rst
> index cef016b2fe..056f556a73 100644
> --- a/doc/guides/howto/debug_troubleshoot.rst
> +++ b/doc/guides/howto/debug_troubleshoot.rst
> @@ -307,8 +307,9 @@ Custom worker function :numref:`dtg_distributor_worker`.
>  
>  #. Configuration issue isolation
>  
> -   * Identify core role using ``rte_eal_lcore_role`` to identify RTE, OFF and
> -     SERVICE. Check performance functions are mapped to run on the cores.
> +   * Identify core role using ``rte_eal_lcore_role`` to identify RTE, OFF,
> +     SERVICE and EXTERNAL. Check performance functions are mapped to run on the
> +     cores.
>  
>     * For high-performance execution logic ensure running it on correct NUMA
>       and non-master core.
> diff --git a/lib/librte_eal/common/eal_common_lcore.c b/lib/librte_eal/common/eal_common_lcore.c
> index 5404922a87..35d6c1295e 100644
> --- a/lib/librte_eal/common/eal_common_lcore.c
> +++ b/lib/librte_eal/common/eal_common_lcore.c
> @@ -6,13 +6,15 @@
>  #include <limits.h>
>  #include <string.h>
>  
> -#include <rte_errno.h>
> -#include <rte_log.h>
> -#include <rte_eal.h>
> -#include <rte_lcore.h>
>  #include <rte_common.h>
>  #include <rte_debug.h>
> +#include <rte_eal.h>
> +#include <rte_errno.h>
> +#include <rte_lcore.h>
> +#include <rte_log.h>
> +#include <rte_spinlock.h>
>  
> +#include "eal_internal_cfg.h"
>  #include "eal_private.h"
>  #include "eal_thread.h"
>  
> @@ -209,3 +211,37 @@ rte_socket_id_by_idx(unsigned int idx)
>  	}
>  	return config->numa_nodes[idx];
>  }
> +
> +rte_spinlock_t external_lcore_lock = RTE_SPINLOCK_INITIALIZER;
> +
> +unsigned int
> +eal_lcore_external_reserve(void)
> +{
> +	struct rte_config *cfg = rte_eal_get_configuration();
> +	unsigned int lcore_id;
> +
> +	rte_spinlock_lock(&external_lcore_lock);
> +	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
> +		if (rte_eal_lcore_role(lcore_id) != ROLE_OFF)
> +			continue;
> +		cfg->lcore_role[lcore_id] = ROLE_EXTERNAL;
> +		cfg->lcore_count++;
> +		break;
> +	}
> +	rte_spinlock_unlock(&external_lcore_lock);
> +
> +	return lcore_id;
> +}
> +
> +void
> +eal_lcore_external_release(unsigned int lcore_id)
> +{
> +	struct rte_config *cfg = rte_eal_get_configuration();
> +
> +	rte_spinlock_lock(&external_lcore_lock);
> +	if (rte_eal_lcore_role(lcore_id) == ROLE_EXTERNAL) {
> +		cfg->lcore_role[lcore_id] = ROLE_OFF;
> +		cfg->lcore_count--;
> +	}
> +	rte_spinlock_unlock(&external_lcore_lock);
> +}
> diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
> index 8a973ca8ac..d57a6ec797 100644
> --- a/lib/librte_eal/common/eal_common_thread.c
> +++ b/lib/librte_eal/common/eal_common_thread.c
> @@ -29,6 +29,7 @@ RTE_DEFINE_PER_LCORE(int, _thread_id) = -1;
>  static RTE_DEFINE_PER_LCORE(unsigned int, _socket_id) =
>  	(unsigned int)SOCKET_ID_ANY;
>  static RTE_DEFINE_PER_LCORE(rte_cpuset_t, _cpuset);
> +static RTE_DEFINE_PER_LCORE(bool, thread_registered);
>  
>  unsigned rte_socket_id(void)
>  {
> @@ -255,3 +256,47 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>  	pthread_join(*thread, NULL);
>  	return -ret;
>  }
> +
> +void
> +rte_thread_register(void)
> +{
> +	unsigned int lcore_id;
> +	rte_cpuset_t cpuset;
> +
> +	/* EAL init flushes all lcores, we can't register before. */
> +	assert(internal_config.init_complete == 1);
> +
> +	if (RTE_PER_LCORE(thread_registered))
> +		return;
> +
> +	if (pthread_getaffinity_np(pthread_self(), sizeof(cpuset),
> +			&cpuset) != 0)
> +		CPU_ZERO(&cpuset);
> +
> +	lcore_id = eal_lcore_external_reserve();
> +	if (lcore_id >= RTE_MAX_LCORE)
> +		lcore_id = LCORE_ID_ANY;
> +
> +	rte_thread_init(lcore_id, &cpuset);
> +
> +	RTE_LOG(DEBUG, EAL, "Registered thread as lcore %u.\n", lcore_id);
> +	RTE_PER_LCORE(thread_registered) = true;
> +}
> +
> +void
> +rte_thread_unregister(void)
> +{
> +	unsigned int lcore_id;
> +
> +	if (!RTE_PER_LCORE(thread_registered))
> +		return;
> +
> +	lcore_id = RTE_PER_LCORE(_lcore_id);
> +	if (lcore_id != LCORE_ID_ANY)
> +		eal_lcore_external_release(lcore_id);
> +
> +	rte_thread_uninit();
> +
> +	RTE_LOG(DEBUG, EAL, "Unregistered thread (was lcore %u).\n", lcore_id);
> +	RTE_PER_LCORE(thread_registered) = false;
> +}
> diff --git a/lib/librte_eal/common/eal_private.h b/lib/librte_eal/common/eal_private.h
> index 869ce183ad..8dd850f68a 100644
> --- a/lib/librte_eal/common/eal_private.h
> +++ b/lib/librte_eal/common/eal_private.h
> @@ -274,6 +274,23 @@ uint64_t get_tsc_freq(void);
>   */
>  uint64_t get_tsc_freq_arch(void);
>  
> +/**
> + * Ask for a free lcore to associate to a non-EAL thread.
> + *
> + * @return
> + *   The id of a lcore with role ROLE_EXTERNAL or RTE_MAX_LCORE if none was
> + *   available.
> + */
> +unsigned int eal_lcore_external_reserve(void);
> +
> +/**
> + * Release an external lcore.
> + *
> + * @param lcore_id
> + *   The lcore with role ROLE_EXTERNAL to release.
> + */
> +void eal_lcore_external_release(unsigned int lcore_id);
> +
>  /**
>   * Prepare physical memory mapping
>   * i.e. hugepages on Linux and
> diff --git a/lib/librte_eal/include/rte_eal.h b/lib/librte_eal/include/rte_eal.h
> index 2edf8c6556..0913d1947c 100644
> --- a/lib/librte_eal/include/rte_eal.h
> +++ b/lib/librte_eal/include/rte_eal.h
> @@ -31,15 +31,6 @@ extern "C" {
>  /* Maximum thread_name length. */
>  #define RTE_MAX_THREAD_NAME_LEN 16
>  
> -/**
> - * The lcore role (used in RTE or not).
> - */
> -enum rte_lcore_role_t {
> -	ROLE_RTE,
> -	ROLE_OFF,
> -	ROLE_SERVICE,
> -};
> -
>  /**
>   * The type of process in a linux, multi-process setup
>   */
> diff --git a/lib/librte_eal/include/rte_lcore.h b/lib/librte_eal/include/rte_lcore.h
> index 5c1d1926e9..d59c4edc67 100644
> --- a/lib/librte_eal/include/rte_lcore.h
> +++ b/lib/librte_eal/include/rte_lcore.h
> @@ -24,6 +24,16 @@ extern "C" {
>  
>  RTE_DECLARE_PER_LCORE(unsigned, _lcore_id);  /**< Per thread "lcore id". */
>  
> +/**
> + * The lcore role (used in RTE or not).
> + */
> +enum rte_lcore_role_t {
> +	ROLE_RTE,
> +	ROLE_OFF,
> +	ROLE_SERVICE,
> +	ROLE_EXTERNAL,
> +};
> +
>  /**
>   * Get a lcore's role.
>   *
> @@ -34,6 +44,20 @@ RTE_DECLARE_PER_LCORE(unsigned, _lcore_id);  /**< Per thread "lcore id". */
>   */
>  enum rte_lcore_role_t rte_eal_lcore_role(unsigned int lcore_id);
>  
> +/**
> + * Test if the core supplied has a specific role
> + *
> + * @param lcore_id
> + *   The identifier of the lcore, which MUST be between 0 and
> + *   RTE_MAX_LCORE-1.
> + * @param role
> + *   The role to be checked against.
> + * @return
> + *   Boolean value: positive if test is true; otherwise returns 0.
> + */
> +int
> +rte_lcore_has_role(unsigned int lcore_id, enum rte_lcore_role_t role);
> +
>  /**
>   * Return the Application thread ID of the execution unit.
>   *
> @@ -256,6 +280,20 @@ int rte_thread_setname(pthread_t id, const char *name);
>  __rte_experimental
>  int rte_thread_getname(pthread_t id, char *name, size_t len);
>  
> +/**
> + * Register current non-EAL thread as a lcore.
> + */
> +__rte_experimental
> +void
> +rte_thread_register(void);
> +
> +/**
> + * Unregister current thread and release lcore if one was associated.
> + */
> +__rte_experimental
> +void
> +rte_thread_unregister(void);
> +
>  /**
>   * Create a control thread.
>   *
> @@ -283,20 +321,6 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>  		const pthread_attr_t *attr,
>  		void *(*start_routine)(void *), void *arg);
>  
> -/**
> - * Test if the core supplied has a specific role
> - *
> - * @param lcore_id
> - *   The identifier of the lcore, which MUST be between 0 and
> - *   RTE_MAX_LCORE-1.
> - * @param role
> - *   The role to be checked against.
> - * @return
> - *   Boolean value: positive if test is true; otherwise returns 0.
> - */
> -int
> -rte_lcore_has_role(unsigned int lcore_id, enum rte_lcore_role_t role);
> -
>  #ifdef __cplusplus
>  }
>  #endif
> diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
> index fdfc3f1a88..f5b68d2815 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -393,4 +393,8 @@ EXPERIMENTAL {
>  	rte_trace_point_lookup;
>  	rte_trace_regexp;
>  	rte_trace_save;
> +
> +	# added in 20.08
> +	rte_thread_register;
> +	rte_thread_unregister;
>  };
Acked-by: Ray Kinsella <mdr@ashroe.eu>