Re: [dpdk-dev] [PATCH v4 1/7] service cores: header and implementation

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Fri, 7 Jul 2017 17:41:01 +0100
> From: Harry van Haaren <harry.van.haaren@intel.com>
> To: dev@dpdk.org
> CC: thomas@monjalon.net, jerin.jacob@caviumnetworks.com,
>  keith.wiles@intel.com, bruce.richardson@intel.com, Harry van Haaren
>  <harry.van.haaren@intel.com>
> Subject: [PATCH v4 1/7] service cores: header and implementation
> X-Mailer: git-send-email 2.7.4
> 
> Add header files, update .map files with new service
> functions, and add the service header to the doxygen
> for building.
> 
> This service header API allows DPDK to use services as
> a concept of something that requires CPU cycles. An example
> is a PMD that runs in software to schedule events, where a
> hardware version exists that does not require a CPU.
> 
> The code presented here is based on an initial RFC:
> http://dpdk.org/ml/archives/dev/2017-May/065207.html
> This was then reworked, and RFC v2 with the changes posted:
> http://dpdk.org/ml/archives/dev/2017-June/067194.html
> 
> This is the fourth iteration of the service core concept,
> with 2 RFCs and this being v2 of the implementation.

Remove above info from the git commit.

> 
> Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
> 
> ---
>  doc/api/doxy-api-index.md                          |   1 +
>  lib/librte_eal/bsdapp/eal/Makefile                 |   1 +
>  lib/librte_eal/bsdapp/eal/rte_eal_version.map      |  22 +
>  lib/librte_eal/common/Makefile                     |   1 +
>  lib/librte_eal/common/eal_common_lcore.c           |   1 +
>  lib/librte_eal/common/include/rte_eal.h            |   4 +
>  lib/librte_eal/common/include/rte_lcore.h          |   3 +-
>  lib/librte_eal/common/include/rte_service.h        | 383 ++++++++++++
>  .../common/include/rte_service_private.h           | 140 +++++
>  lib/librte_eal/common/rte_service.c                | 687 +++++++++++++++++++++
>  lib/librte_eal/linuxapp/eal/Makefile               |   1 +
>  lib/librte_eal/linuxapp/eal/eal_thread.c           |   9 +-
>  lib/librte_eal/linuxapp/eal/rte_eal_version.map    |  22 +
>  13 files changed, 1273 insertions(+), 2 deletions(-)
>  create mode 100644 lib/librte_eal/common/include/rte_service.h
>  create mode 100644 lib/librte_eal/common/include/rte_service_private.h
>  create mode 100644 lib/librte_eal/common/rte_service.c
> 
> diff --git a/doc/api/doxy-api-index.md b/doc/api/doxy-api-index.md
> index 3b83288..e2abdf4 100644
> --- a/doc/api/doxy-api-index.md
> +++ b/doc/api/doxy-api-index.md
> @@ -159,6 +159,7 @@ There are many libraries, so their headers may be grouped by topics:
>    [common]             (@ref rte_common.h),
>    [ABI compat]         (@ref rte_compat.h),
>    [keepalive]          (@ref rte_keepalive.h),
> +  [service cores]      (@ref rte_service.h),
>    [device metrics]     (@ref rte_metrics.h),
>    [bitrate statistics] (@ref rte_bitrate.h),
>    [latency statistics] (@ref rte_latencystats.h),


Fix the below mentioned documentation warning.

+/export/dpdk.org/lib/librte_eal/common/include/rte_service.h:338:
warning: argument 'enabled' of command @param is not found in the
argument list of rte_service_set_stats_enable(int enable)
+/export/dpdk.org/lib/librte_eal/common/include/rte_service.h:346:
warning: The following parameters of rte_service_set_stats_enable(int
enable) are not documented:
+  parameter 'enable'                                                           
+/export/dpdk.org/lib/librte_eal/common/include/rte_service.h:349:
warning: argument 'The' of command @param is not found in the argument
list of rte_service_lcore_list(uint32_t array[], uint32_t n)
+/export/dpdk.org/lib/librte_eal/common/include/rte_service.h:367:
warning: The following parameters of rte_service_lcore_list(uint32_t
array[], uint32_t n) are not documented:
+  parameter 'n'      

command to reproduce:
./devtools/test-build.sh -j8 x86_64-native-linuxapp-gcc+shared x86_64-native-linuxapp-gcc+debug



>  } DPDK_17.08;
> diff --git a/lib/librte_eal/common/Makefile b/lib/librte_eal/common/Makefile
> index f2fe052..942f03c 100644
> --- a/lib/librte_eal/common/Makefile
> +++ b/lib/librte_eal/common/Makefile
> @@ -41,6 +41,7 @@ INC += rte_eal_memconfig.h rte_malloc_heap.h
>  INC += rte_hexdump.h rte_devargs.h rte_bus.h rte_dev.h rte_vdev.h
>  INC += rte_pci_dev_feature_defs.h rte_pci_dev_features.h
>  INC += rte_malloc.h rte_keepalive.h rte_time.h
> +INC += rte_service.h rte_service_private.h

IMO, We don't need to expose rte_service_private.h to application. If
you agree, add the following or similar change

diff --git a/drivers/event/sw/Makefile b/drivers/event/sw/Makefile
index 857a87cc5..442652e93 100644
--- a/drivers/event/sw/Makefile
+++ b/drivers/event/sw/Makefile
@@ -36,6 +36,8 @@ LIB = librte_pmd_sw_event.a
 # build flags
 CFLAGS += -O3
 CFLAGS += $(WERROR_FLAGS)
+CFLAGS += -I$(RTE_SDK)/lib/librte_eal/common/include/
+
 # for older GCC versions, allow us to initialize an event using
 # designated initializers.
 ifeq ($(CONFIG_RTE_TOOLCHAIN_GCC),y)
diff --git a/lib/librte_eal/common/Makefile
b/lib/librte_eal/common/Makefile
index 942f03cdd..ea6c1f8f1 100644
--- a/lib/librte_eal/common/Makefile
+++ b/lib/librte_eal/common/Makefile
@@ -41,7 +41,7 @@ INC += rte_eal_memconfig.h rte_malloc_heap.h
 INC += rte_hexdump.h rte_devargs.h rte_bus.h rte_dev.h rte_vdev.h
 INC += rte_pci_dev_feature_defs.h rte_pci_dev_features.h
 INC += rte_malloc.h rte_keepalive.h rte_time.h
-INC += rte_service.h rte_service_private.h
+INC += rte_service.h

diff --git a/test/test/Makefile b/test/test/Makefile
index 42d9a49e2..b603b6563 100644
--- a/test/test/Makefile
+++ b/test/test/Makefile
@@ -152,6 +152,7 @@ SRCS-y += test_version.c
 SRCS-y += test_func_reentrancy.c
 
 SRCS-y += test_service_cores.c
+CFLAGS_test_service_cores.o += -I$(RTE_SDK)/lib/librte_eal/common/include/
 
 SRCS-$(CONFIG_RTE_LIBRTE_CMDLINE) += test_cmdline.c
 SRCS-$(CONFIG_RTE_LIBRTE_CMDLINE) += test_cmdline_num.



>  
>  GENERIC_INC := rte_atomic.h rte_byteorder.h rte_cycles.h rte_prefetch.h
>  GENERIC_INC += rte_spinlock.h rte_memcpy.h rte_cpuflags.h rte_rwlock.h
> diff --git a/lib/librte_eal/common/eal_common_lcore.c b/lib/librte_eal/common/eal_common_lcore.c
> index 84fa0cb..0db1555 100644
> --- a/lib/librte_eal/common/eal_common_lcore.c
> +++ b/lib/librte_eal/common/eal_common_lcore.c
> @@ -81,6 +81,7 @@ rte_eal_cpu_init(void)
>  
>  		/* By default, each detected core is enabled */
>  		config->lcore_role[lcore_id] = ROLE_RTE;
> +		lcore_config[lcore_id].core_role = ROLE_RTE;
>  		lcore_config[lcore_id].core_id = eal_cpu_core_id(lcore_id);
>  		lcore_config[lcore_id].socket_id = eal_cpu_socket_id(lcore_id);
>  		if (lcore_config[lcore_id].socket_id >= RTE_MAX_NUMA_NODES) {
> diff --git a/lib/librte_eal/common/include/rte_eal.h b/lib/librte_eal/common/include/rte_eal.h
> index abf020b..4dd0518 100644
> --- a/lib/librte_eal/common/include/rte_eal.h
> +++ b/lib/librte_eal/common/include/rte_eal.h
> @@ -61,6 +61,7 @@ extern "C" {
>  enum rte_lcore_role_t {
>  	ROLE_RTE,
>  	ROLE_OFF,
> +	ROLE_SERVICE,
>  };
>  
> +
> +#define SERVICE_F_REGISTERED 0
> +
> +/* runstates for services and lcores, denoting if they are active or not */
> +#define RUNSTATE_STOPPED 0
> +#define RUNSTATE_RUNNING 1
> +
> +/* internal representation of a service */
> +struct rte_service_spec_impl {
> +	/* public part of the struct */
> +	struct rte_service_spec spec;
> +
> +	/* atomic lock that when set indicates a service core is currently
> +	 * running this service callback. When not set, a core may take the
> +	 * lock and then run the service callback.
> +	 */
> +	rte_atomic32_t execute_lock;
> +
> +	/* API set/get-able variables */
> +	int32_t runstate;
> +	uint8_t internal_flags;
> +
> +	/* per service statistics */
> +	uint32_t num_mapped_cores;
> +	uint64_t calls;
> +	uint64_t cycles_spent;
> +} __rte_cache_aligned;
> +
> +/* the internal values of a service core */
> +struct core_state {

Change to lcore_state.

> +	/* map of services IDs are run on this core */
> +	uint64_t service_mask;
> +	uint8_t runstate; /* running or stopped */
> +	uint8_t is_service_core; /* set if core is currently a service core */
> +	uint8_t collect_statistics; /* if set, measure cycle counts */
> +
> +	/* extreme statistics */
> +	uint64_t calls_per_service[RTE_SERVICE_NUM_MAX];
> +} __rte_cache_aligned;
> +
> +static uint32_t rte_service_count;
> +static struct rte_service_spec_impl *rte_services;
> +static struct core_state *cores_state;
> +static uint32_t rte_service_library_initialized;
> +
> +int32_t rte_service_init(void)
> +{
> +	if (rte_service_library_initialized) {
> +		printf("service library init() called, init flag %d\n",
> +			rte_service_library_initialized);
> +		return -EALREADY;
> +	}
> +
> +	rte_services = rte_calloc("rte_services", RTE_SERVICE_NUM_MAX,
> +			sizeof(struct rte_service_spec_impl),
> +			RTE_CACHE_LINE_SIZE);
> +	if (!rte_services) {
> +		printf("error allocating rte services array\n");
> +		return -ENOMEM;
> +	}
> +
> +	cores_state = rte_calloc("rte_service_core_states", RTE_MAX_LCORE,
> +			sizeof(struct core_state), RTE_CACHE_LINE_SIZE);
> +	if (!cores_state) {
> +		printf("error allocating core states array\n");
> +		return -ENOMEM;
> +	}
> +
> +	int i;
> +	int count = 0;
> +	struct rte_config *cfg = rte_eal_get_configuration();
> +	for (i = 0; i < RTE_MAX_LCORE; i++) {
> +		if (lcore_config[i].core_role == ROLE_SERVICE) {
> +			if ((unsigned int)i == cfg->master_lcore)
> +				continue;
> +			rte_service_lcore_add(i);
> +			count++;
> +		}
> +	}
> +
> +	rte_service_library_initialized = 1;
> +	return 0;
> +}
> +
> +void rte_service_set_stats_enable(int enabled)

IMO, It should be per service  i.e
rte_service_set_stats_enable(const struct rte_service_spec *spec, int enable)

> +{
> +	uint32_t i;
> +	for (i = 0; i < RTE_MAX_LCORE; i++)
> +		cores_state[i].collect_statistics = enabled;
> +}
> +
> +/* returns 1 if service is registered and has not been unregistered
> + * Returns 0 if service never registered, or has been unregistered
> + */
> +static inline int
> +service_valid(uint32_t id) {
> +	return !!(rte_services[id].internal_flags &
> +		 (1 << SERVICE_F_REGISTERED));
> +}
> +
> +uint32_t
> +rte_service_get_count(void)
> +{
> +	return rte_service_count;
> +}
> +
> +struct rte_service_spec *
> +rte_service_get_by_id(uint32_t id)
> +{
> +	struct rte_service_spec *service = NULL;
> +	if (id < rte_service_count)
> +		service = (struct rte_service_spec *)&rte_services[id];
> +
> +	return service;
> +}
> +
> +struct rte_service_spec *rte_service_get_by_name(const char *name)
> +{
> +	struct rte_service_spec *service = NULL;
> +	int i;
> +	for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) {
> +		if (service_valid(i) &&
> +				strcmp(name, rte_services[i].spec.name) == 0) {
> +			service = (struct rte_service_spec *)&rte_services[i];
> +			break;
> +		}
> +	}
> +
> +	return service;
> +}
> +
> +const char *
> +rte_service_get_name(const struct rte_service_spec *service)
> +{
> +	return service->name;
> +}
> +
> +int32_t
> +rte_service_probe_capability(const struct rte_service_spec *service,
> +			     uint32_t capability)
> +{
> +	return service->capabilities & capability;
> +}
> +
> +int32_t
> +rte_service_is_running(const struct rte_service_spec *spec)
> +{
> +	const struct rte_service_spec_impl *impl =
> +		(const struct rte_service_spec_impl *)spec;
> +	if (!impl)
> +		return -EINVAL;
> +
> +	return (impl->runstate == RUNSTATE_RUNNING) &&
> +		(impl->num_mapped_cores > 0);
> +}
> +
> +int32_t
> +rte_service_register(const struct rte_service_spec *spec)
> +{
> +	uint32_t i;
> +	int32_t free_slot = -1;
> +
> +	if (spec->callback == NULL || strlen(spec->name) == 0)
> +		return -EINVAL;
> +
> +	for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) {
> +		if (!service_valid(i)) {
> +			free_slot = i;
> +			break;
> +		}
> +	}
> +
> +	if ((free_slot < 0) || (i == RTE_SERVICE_NUM_MAX))
> +		return -ENOSPC;
> +
> +	struct rte_service_spec_impl *s = &rte_services[free_slot];
> +	s->spec = *spec;
> +	s->internal_flags |= (1 << SERVICE_F_REGISTERED);
> +
> +	rte_smp_wmb();
> +	rte_service_count++;
> +
> +	return 0;
> +}
> +
> +int32_t
> +rte_service_unregister(struct rte_service_spec *spec)
> +{
> +	struct rte_service_spec_impl *s = NULL;
> +	struct rte_service_spec_impl *spec_impl =
> +		(struct rte_service_spec_impl *)spec;
> +
> +	uint32_t i;
> +	uint32_t service_id;
> +	for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) {
> +		if (&rte_services[i] == spec_impl) {
> +			s = spec_impl;
> +			service_id = i;
> +			break;
> +		}
> +	}
> +
> +	if (!s)
> +		return -EINVAL;
> +
> +	rte_service_count--;
> +	rte_smp_wmb();
> +
> +	s->internal_flags &= ~(1 << SERVICE_F_REGISTERED);
> +
> +	for (i = 0; i < RTE_MAX_LCORE; i++)
> +		cores_state[i].service_mask &= ~(1 << service_id);
> +
> +	memset(&rte_services[service_id], 0,
> +			sizeof(struct rte_service_spec_impl));
> +
> +	return 0;
> +}
> +
> +int32_t
> +rte_service_start(struct rte_service_spec *service)
> +{
> +	struct rte_service_spec_impl *s =
> +		(struct rte_service_spec_impl *)service;
> +	s->runstate = RUNSTATE_RUNNING;
> +	rte_smp_wmb();
> +	return 0;
> +}
> +
> +int32_t
> +rte_service_stop(struct rte_service_spec *service)
> +{
> +	struct rte_service_spec_impl *s =
> +		(struct rte_service_spec_impl *)service;
> +	s->runstate = RUNSTATE_STOPPED;
> +	rte_smp_wmb();
> +	return 0;
> +}
> +
> +static int32_t
> +rte_service_runner_func(void *arg)
> +{
> +	RTE_SET_USED(arg);
> +	uint32_t i;
> +	const int lcore = rte_lcore_id();
> +	struct core_state *cs = &cores_state[lcore];
> +
> +	while (cores_state[lcore].runstate == RUNSTATE_RUNNING) {
> +		const uint64_t service_mask = cs->service_mask;
> +		for (i = 0; i < rte_service_count; i++) {
> +			struct rte_service_spec_impl *s = &rte_services[i];
> +			if (s->runstate != RUNSTATE_RUNNING ||
> +					!(service_mask & (1 << i)))
> +				continue;
> +
> +			/* check if this is the only core mapped, else use
> +			 * atomic to serialize cores mapped to this service
> +			 */
> +			uint32_t *lock = (uint32_t *)&s->execute_lock;
> +			if ((s->spec.capabilities & RTE_SERVICE_CAP_MT_SAFE) ||
> +					(s->num_mapped_cores == 1 ||
> +					rte_atomic32_cmpset(lock, 0, 1))) {
> +				void *userdata = s->spec.callback_userdata;
> +
> +				if (cs->collect_statistics) {
> +					uint64_t start = rte_rdtsc();
> +					s->spec.callback(userdata);
> +					uint64_t end = rte_rdtsc();
> +					s->cycles_spent += end - start;
> +					cs->calls_per_service[i]++;
> +					s->calls++;
> +				} else
> +					s->spec.callback(userdata);
> +
> +				if ((s->spec.capabilities &
> +						RTE_SERVICE_CAP_MT_SAFE) == 0 &&
> +						s->num_mapped_cores > 1)

How about computing the non rte_atomic32_cmpset() mode value first and
using in both place i.e here and in the top "if" loop

	const int need_cmpset = (s->spec.capabilities & RTE_SERVICE_CAP_MT_SAFE)...
	if (need_cmpset || rte_atomic32_cmpset(lock, 0, 1))
	..
	if (need_cmpset)
		rte_atomic32_clear()..


> +					rte_atomic32_clear(&s->execute_lock);
> +			}
> +		}
> +
> +		rte_smp_rmb();
> +	}
> +
> +	lcore_config[lcore].state = WAIT;
> +
> +	return 0;
> +}
> +
> +int32_t
> +rte_service_lcore_count(void)
> +{
> +	int32_t count = 0;
> +	uint32_t i;
> +	for (i = 0; i < RTE_MAX_LCORE; i++)
> +		count += cores_state[i].is_service_core;
> +	return count;
> +}
> +
> +int32_t
> +rte_service_lcore_list(uint32_t array[], uint32_t n)
> +{
> +	uint32_t count = rte_service_lcore_count();
> +	if (count > n)
> +		return -ENOMEM;
> +
> +	if (!array)
> +		return -EINVAL;
> +
> +	uint32_t i;
> +	uint32_t idx = 0;
> +	for (i = 0; i < RTE_MAX_LCORE; i++) {
> +		struct core_state *cs = &cores_state[i];
> +		if (cs->is_service_core) {
> +			array[idx] = i;
> +			idx++;
> +		}
> +	}
> +
> +	return count;
> +}
> +
> +int32_t
> +rte_service_set_default_mapping(void)
> +{
> +	/* create a default mapping from cores to services, then start the
> +	 * services to make them transparent to unaware applications.
> +	 */
> +	uint32_t i;
> +	int ret;
> +	uint32_t count = rte_service_get_count();
> +
> +	int32_t lcore_iter = 0;
> +	uint32_t ids[RTE_MAX_LCORE];
> +	int32_t lcore_count = rte_service_lcore_list(ids, RTE_MAX_LCORE);
> +
> +	for (i = 0; i < count; i++) {
> +		struct rte_service_spec *s = rte_service_get_by_id(i);
> +		if (!s)
> +			return -EINVAL;
> +
> +		/* if no lcores available as services cores, don't setup map.
> +		 * This means app logic must add cores, and setup mappings
> +		 */
> +		if (lcore_count > 0) {


> +			/* do 1:1 core mapping here, with each service getting
> +			 * assigned a single core by default. Adding multiple
> +			 * services should multiplex to a single core, or 1:1
> +			 * if services == cores
> +			 */
> +			ret = rte_service_enable_on_lcore(s, ids[lcore_iter]);
> +			if (ret)
> +				return -ENODEV;
> +		}
> +
> +		lcore_iter++;
> +		if (lcore_iter >= lcore_count)
> +			lcore_iter = 0;
> +
> +		ret = rte_service_start(s);

IMO, we don't need to start the service if lcore_count == 0. How about
moving the "if (lcore_count > 0)" check on top of for the loop and exist
from the function if lcore_count == 0.


> +		if (ret)
> +			return -ENOEXEC;
> +	}
> +
> +	return 0;
> +}
> +
> +static int32_t
> +service_update(struct rte_service_spec *service, uint32_t lcore,
> +		uint32_t *set, uint32_t *enabled)
> +{
> +	uint32_t i;
> +	int32_t sid = -1;
> +
> +	for (i = 0; i < RTE_SERVICE_NUM_MAX; i++) {
> +		if ((struct rte_service_spec *)&rte_services[i] == service &&
> +				service_valid(i)) {
> +			sid = i;
> +			break;
> +		}
> +	}
> +
> +	if (sid == -1 || lcore >= RTE_MAX_LCORE)
> +		return -EINVAL;
> +
> +	if (!cores_state[lcore].is_service_core)
> +		return -EINVAL;
> +
> +	if (set) {
> +		if (*set) {
> +			cores_state[lcore].service_mask |=  (1 << sid);
> +			rte_services[sid].num_mapped_cores++;
> +		} else {
> +			cores_state[lcore].service_mask &= ~(1 << sid);
> +			rte_services[sid].num_mapped_cores--;
> +		}
> +	}
> +
> +	if (enabled)
> +		*enabled = (cores_state[lcore].service_mask & (1 << sid));
> +
> +	rte_smp_wmb();
> +
> +	return 0;
> +}
> +
> +int32_t rte_service_get_enabled_on_lcore(struct rte_service_spec *service,
> +					uint32_t lcore)
> +{
> +	uint32_t enabled;
> +	int ret = service_update(service, lcore, 0, &enabled);
> +	if (ret == 0)
> +		return enabled;
> +	return -EINVAL;
> +}
> +
> +int32_t
> +rte_service_enable_on_lcore(struct rte_service_spec *service, uint32_t lcore)
> +{
> +	uint32_t on = 1;
> +	return service_update(service, lcore, &on, 0);
> +}
> +
> +int32_t
> +rte_service_disable_on_lcore(struct rte_service_spec *service, uint32_t lcore)
> +{
> +	uint32_t off = 0;
> +	return service_update(service, lcore, &off, 0);
> +}
> +
> +int32_t rte_service_lcore_reset_all(void)
> +{
> +	/* loop over cores, reset all to mask 0 */
> +	uint32_t i;
> +	for (i = 0; i < RTE_MAX_LCORE; i++) {
> +		cores_state[i].service_mask = 0;
> +		cores_state[i].is_service_core = 0;
> +		cores_state[i].runstate = RUNSTATE_STOPPED;
> +	}
> +	for (i = 0; i < RTE_SERVICE_NUM_MAX; i++)
> +		rte_services[i].num_mapped_cores = 0;
> +
> +	rte_smp_wmb();
> +
> +	return 0;
> +}
> +
> +static void
> +set_lcore_state(uint32_t lcore, int32_t state)
> +{
> +	/* mark core state in hugepage backed config */
> +	struct rte_config *cfg = rte_eal_get_configuration();
> +	cfg->lcore_role[lcore] = state;
> +
> +	/* mark state in process local lcore_config */
> +	lcore_config[lcore].core_role = state;
> +
> +	/* update per-lcore optimized state tracking */
> +	cores_state[lcore].is_service_core = (state == ROLE_SERVICE);
> +}
> +
> +int32_t
> +rte_service_lcore_add(uint32_t lcore)
> +{
> +	if (lcore >= RTE_MAX_LCORE)
> +		return -EINVAL;
> +	if (cores_state[lcore].is_service_core)
> +		return -EALREADY;
> +
> +	set_lcore_state(lcore, ROLE_SERVICE);
> +
> +	/* ensure that after adding a core the mask and state are defaults */
> +	cores_state[lcore].service_mask = 0;
> +	cores_state[lcore].runstate = RUNSTATE_STOPPED;

If worker core can call rte_service_lcore_add() then add rte_smp_wmb()
here. Applies to rte_service_lcore_del() as well.