[dpdk-dev] [PATCH v2 8/9] eal: add lcore iterators

[David Marchand <david.marchand@redhat.com>]

Add a helper to iterate all lcores.
The iterator callback is read-only wrt the lcores list.

Implement a dump function on top of this for debugging.

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
Changes since v1:
- introduced lcore iterators and implemented rte_lcore_dump,
  this iterator mechanism can then be used outside of EAL,

---
 lib/librte_eal/common/eal_common_lcore.c  | 77 ++++++++++++++++++++---
 lib/librte_eal/common/eal_common_thread.c | 16 +++--
 lib/librte_eal/common/eal_thread.h        | 13 +++-
 lib/librte_eal/freebsd/eal.c              |  2 +-
 lib/librte_eal/freebsd/eal_thread.c       |  2 +-
 lib/librte_eal/include/rte_lcore.h        | 47 +++++++++++++-
 lib/librte_eal/linux/eal.c                |  2 +-
 lib/librte_eal/linux/eal_thread.c         |  2 +-
 lib/librte_eal/rte_eal_version.map        |  2 +
 9 files changed, 140 insertions(+), 23 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_lcore.c b/lib/librte_eal/common/eal_common_lcore.c
index 5140026b6c..2524356a88 100644
--- a/lib/librte_eal/common/eal_common_lcore.c
+++ b/lib/librte_eal/common/eal_common_lcore.c
@@ -12,7 +12,7 @@
 #include <rte_errno.h>
 #include <rte_lcore.h>
 #include <rte_log.h>
-#include <rte_spinlock.h>
+#include <rte_rwlock.h>
 
 #include "eal_private.h"
 #include "eal_thread.h"
@@ -222,7 +222,7 @@ rte_socket_id_by_idx(unsigned int idx)
 	return config->numa_nodes[idx];
 }
 
-static rte_spinlock_t lcore_lock = RTE_SPINLOCK_INITIALIZER;
+static rte_rwlock_t lcore_lock = RTE_RWLOCK_INITIALIZER;
 struct lcore_callback {
 	TAILQ_ENTRY(lcore_callback) next;
 	char *name;
@@ -271,7 +271,7 @@ rte_lcore_callback_register(const char *name, rte_lcore_init_cb init,
 	callback->init = init;
 	callback->uninit = uninit;
 	callback->arg = arg;
-	rte_spinlock_lock(&lcore_lock);
+	rte_rwlock_write_lock(&lcore_lock);
 	if (callback->init == NULL)
 		goto no_init;
 	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
@@ -297,7 +297,7 @@ rte_lcore_callback_register(const char *name, rte_lcore_init_cb init,
 		callback->name, callback->init == NULL ? "NO " : "",
 		callback->uninit == NULL ? "NO " : "");
 out:
-	rte_spinlock_unlock(&lcore_lock);
+	rte_rwlock_write_unlock(&lcore_lock);
 	return callback;
 }
 
@@ -308,7 +308,7 @@ rte_lcore_callback_unregister(void *handle)
 	struct lcore_callback *callback = handle;
 	unsigned int lcore_id;
 
-	rte_spinlock_lock(&lcore_lock);
+	rte_rwlock_write_lock(&lcore_lock);
 	if (callback->uninit == NULL)
 		goto no_uninit;
 	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
@@ -318,7 +318,7 @@ rte_lcore_callback_unregister(void *handle)
 	}
 no_uninit:
 	TAILQ_REMOVE(&lcore_callbacks, callback, next);
-	rte_spinlock_unlock(&lcore_lock);
+	rte_rwlock_write_unlock(&lcore_lock);
 	RTE_LOG(DEBUG, EAL, "Unregistered lcore callback %s-%p.\n",
 		callback->name, callback->arg);
 	free(callback->name);
@@ -333,7 +333,7 @@ eal_lcore_non_eal_allocate(void)
 	struct lcore_callback *prev;
 	unsigned int lcore_id;
 
-	rte_spinlock_lock(&lcore_lock);
+	rte_rwlock_write_lock(&lcore_lock);
 	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
 		if (cfg->lcore_role[lcore_id] != ROLE_OFF)
 			continue;
@@ -365,7 +365,7 @@ eal_lcore_non_eal_allocate(void)
 		goto out;
 	}
 out:
-	rte_spinlock_unlock(&lcore_lock);
+	rte_rwlock_write_unlock(&lcore_lock);
 	return lcore_id;
 }
 
@@ -375,7 +375,7 @@ eal_lcore_non_eal_release(unsigned int lcore_id)
 	struct rte_config *cfg = rte_eal_get_configuration();
 	struct lcore_callback *callback;
 
-	rte_spinlock_lock(&lcore_lock);
+	rte_rwlock_write_lock(&lcore_lock);
 	if (cfg->lcore_role[lcore_id] != ROLE_NON_EAL)
 		goto out;
 	TAILQ_FOREACH(callback, &lcore_callbacks, next)
@@ -383,5 +383,62 @@ eal_lcore_non_eal_release(unsigned int lcore_id)
 	cfg->lcore_role[lcore_id] = ROLE_OFF;
 	cfg->lcore_count--;
 out:
-	rte_spinlock_unlock(&lcore_lock);
+	rte_rwlock_write_unlock(&lcore_lock);
+}
+
+int
+rte_lcore_iterate(rte_lcore_iterate_cb cb, void *arg)
+{
+	struct rte_config *cfg = rte_eal_get_configuration();
+	unsigned int lcore_id;
+	int ret = 0;
+
+	rte_rwlock_read_lock(&lcore_lock);
+	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
+		if (cfg->lcore_role[lcore_id] == ROLE_OFF)
+			continue;
+		ret = cb(lcore_id, arg);
+		if (ret != 0)
+			break;
+	}
+	rte_rwlock_read_unlock(&lcore_lock);
+	return ret;
+}
+
+static int
+lcore_dump_cb(unsigned int lcore_id, void *arg)
+{
+	struct rte_config *cfg = rte_eal_get_configuration();
+	char cpuset[RTE_CPU_AFFINITY_STR_LEN];
+	const char *role;
+	FILE *f = arg;
+	int ret;
+
+	switch (cfg->lcore_role[lcore_id]) {
+	case ROLE_RTE:
+		role = "RTE";
+		break;
+	case ROLE_SERVICE:
+		role = "SERVICE";
+		break;
+	case ROLE_NON_EAL:
+		role = "NON_EAL";
+		break;
+	default:
+		role = "UNKNOWN";
+		break;
+	}
+
+	ret = eal_thread_dump_affinity(&lcore_config[lcore_id].cpuset, cpuset,
+		sizeof(cpuset));
+	fprintf(f, "lcore %u, socket %u, role %s, cpuset %s%s\n", lcore_id,
+		rte_lcore_to_socket_id(lcore_id), role, cpuset,
+		ret == 0 ? "" : "...");
+	return 0;
+}
+
+void
+rte_lcore_dump(FILE *f)
+{
+	rte_lcore_iterate(lcore_dump_cb, f);
 }
diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
index 338194832b..5dc0b12f42 100644
--- a/lib/librte_eal/common/eal_common_thread.c
+++ b/lib/librte_eal/common/eal_common_thread.c
@@ -104,17 +104,14 @@ rte_thread_get_affinity(rte_cpuset_t *cpusetp)
 }
 
 int
-eal_thread_dump_affinity(char *str, unsigned size)
+eal_thread_dump_affinity(rte_cpuset_t *cpuset, char *str, unsigned int size)
 {
-	rte_cpuset_t cpuset;
 	unsigned cpu;
 	int ret;
 	unsigned int out = 0;
 
-	rte_thread_get_affinity(&cpuset);
-
 	for (cpu = 0; cpu < CPU_SETSIZE; cpu++) {
-		if (!CPU_ISSET(cpu, &cpuset))
+		if (!CPU_ISSET(cpu, cpuset))
 			continue;
 
 		ret = snprintf(str + out,
@@ -137,6 +134,15 @@ eal_thread_dump_affinity(char *str, unsigned size)
 	return ret;
 }
 
+int
+eal_thread_dump_current_affinity(char *str, unsigned int size)
+{
+	rte_cpuset_t cpuset;
+
+	rte_thread_get_affinity(&cpuset);
+	return eal_thread_dump_affinity(&cpuset, str, size);
+}
+
 void
 rte_thread_init(unsigned int lcore_id, rte_cpuset_t *cpuset)
 {
diff --git a/lib/librte_eal/common/eal_thread.h b/lib/librte_eal/common/eal_thread.h
index 4ecd8fd53a..13ec252e01 100644
--- a/lib/librte_eal/common/eal_thread.h
+++ b/lib/librte_eal/common/eal_thread.h
@@ -47,13 +47,15 @@ unsigned eal_cpu_socket_id(unsigned cpu_id);
 #define RTE_CPU_AFFINITY_STR_LEN            256
 
 /**
- * Dump the current pthread cpuset.
+ * Dump the cpuset as a human readable string.
  * This function is private to EAL.
  *
  * Note:
  *   If the dump size is greater than the size of given buffer,
  *   the string will be truncated and with '\0' at the end.
  *
+ * @param cpuset
+ *   The CPU affinity object to dump.
  * @param str
  *   The string buffer the cpuset will dump to.
  * @param size
@@ -62,6 +64,13 @@ unsigned eal_cpu_socket_id(unsigned cpu_id);
  *   0 for success, -1 if truncation happens.
  */
 int
-eal_thread_dump_affinity(char *str, unsigned size);
+eal_thread_dump_affinity(rte_cpuset_t *cpuset, char *str, unsigned int size);
+
+/**
+ * Dump the current thread cpuset.
+ * This is a wrapper on eal_thread_dump_affinity().
+ */
+int
+eal_thread_dump_current_affinity(char *str, unsigned int size);
 
 #endif /* EAL_THREAD_H */
diff --git a/lib/librte_eal/freebsd/eal.c b/lib/librte_eal/freebsd/eal.c
index b5ea11df16..69a6f7d8c4 100644
--- a/lib/librte_eal/freebsd/eal.c
+++ b/lib/librte_eal/freebsd/eal.c
@@ -886,7 +886,7 @@ rte_eal_init(int argc, char **argv)
 	rte_thread_init(rte_config.master_lcore,
 		&lcore_config[rte_config.master_lcore].cpuset);
 
-	ret = eal_thread_dump_affinity(cpuset, sizeof(cpuset));
+	ret = eal_thread_dump_current_affinity(cpuset, sizeof(cpuset));
 
 	RTE_LOG(DEBUG, EAL, "Master lcore %u is ready (tid=%p;cpuset=[%s%s])\n",
 		rte_config.master_lcore, thread_id, cpuset,
diff --git a/lib/librte_eal/freebsd/eal_thread.c b/lib/librte_eal/freebsd/eal_thread.c
index c1fb8eb2d8..b1a3619f51 100644
--- a/lib/librte_eal/freebsd/eal_thread.c
+++ b/lib/librte_eal/freebsd/eal_thread.c
@@ -92,7 +92,7 @@ eal_thread_loop(__rte_unused void *arg)
 
 	rte_thread_init(lcore_id, &lcore_config[lcore_id].cpuset);
 
-	ret = eal_thread_dump_affinity(cpuset, sizeof(cpuset));
+	ret = eal_thread_dump_current_affinity(cpuset, sizeof(cpuset));
 	RTE_LOG(DEBUG, EAL, "lcore %u is ready (tid=%p;cpuset=[%s%s])\n",
 		lcore_id, thread_id, cpuset, ret == 0 ? "" : "...");
 
diff --git a/lib/librte_eal/include/rte_lcore.h b/lib/librte_eal/include/rte_lcore.h
index 27b29a1f87..4dee7cbcd7 100644
--- a/lib/librte_eal/include/rte_lcore.h
+++ b/lib/librte_eal/include/rte_lcore.h
@@ -261,8 +261,8 @@ typedef void (*rte_lcore_uninit_cb)(unsigned int lcore_id, void *arg);
  * If this step succeeds, the callbacks are put in the lcore callbacks list
  * that will get called for each lcore allocation/release.
  *
- * Note: callbacks execution is serialised under a lock protecting the lcores
- * and callbacks list.
+ * Note: callbacks execution is serialised under a write lock protecting the
+ * lcores and callbacks list.
  *
  * @param name
  *   A name serving as a small description for this callback.
@@ -297,6 +297,49 @@ __rte_experimental
 void
 rte_lcore_callback_unregister(void *handle);
 
+/**
+ * Callback prototype for iterating over lcores.
+ *
+ * @param lcore_id
+ *   The lcore to consider.
+ * @param arg
+ *   An opaque pointer coming from the caller.
+ * @return
+ *   - 0 lets the iteration continue.
+ *   - !0 makes the iteration stop.
+ */
+typedef int (*rte_lcore_iterate_cb)(unsigned int lcore_id, void *arg);
+
+/**
+ * Iterate on all active lcores (ROLE_RTE, ROLE_SERVICE and ROLE_NON_EAL).
+ * No modification on the lcore states is allowed in the callback.
+ *
+ * Note: as opposed to init/uninit callbacks, iteration callbacks can be
+ * invoked in parallel as they are run under a read lock protecting the lcores
+ * and callbacks list.
+ *
+ * @param cb
+ *   The callback that gets passed each lcore.
+ * @param arg
+ *   An opaque pointer passed to cb.
+ * @return
+ *   Same return code as the callback last invocation (see rte_lcore_iterate_cb
+ *   description).
+ */
+__rte_experimental
+int
+rte_lcore_iterate(rte_lcore_iterate_cb cb, void *arg);
+
+/**
+ * List all lcores.
+ *
+ * @param f
+ *   The output stream where the dump should be sent.
+ */
+__rte_experimental
+void
+rte_lcore_dump(FILE *f);
+
 /**
  * Set core affinity of the current thread.
  * Support both EAL and non-EAL thread and update TLS.
diff --git a/lib/librte_eal/linux/eal.c b/lib/librte_eal/linux/eal.c
index 8638376b8a..2f0efd7cd3 100644
--- a/lib/librte_eal/linux/eal.c
+++ b/lib/librte_eal/linux/eal.c
@@ -1214,7 +1214,7 @@ rte_eal_init(int argc, char **argv)
 	rte_thread_init(rte_config.master_lcore,
 		&lcore_config[rte_config.master_lcore].cpuset);
 
-	ret = eal_thread_dump_affinity(cpuset, sizeof(cpuset));
+	ret = eal_thread_dump_current_affinity(cpuset, sizeof(cpuset));
 	RTE_LOG(DEBUG, EAL, "Master lcore %u is ready (tid=%zx;cpuset=[%s%s])\n",
 		rte_config.master_lcore, (uintptr_t)thread_id, cpuset,
 		ret == 0 ? "" : "...");
diff --git a/lib/librte_eal/linux/eal_thread.c b/lib/librte_eal/linux/eal_thread.c
index 07aec0c44d..22d9bc8c01 100644
--- a/lib/librte_eal/linux/eal_thread.c
+++ b/lib/librte_eal/linux/eal_thread.c
@@ -92,7 +92,7 @@ eal_thread_loop(__rte_unused void *arg)
 
 	rte_thread_init(lcore_id, &lcore_config[lcore_id].cpuset);
 
-	ret = eal_thread_dump_affinity(cpuset, sizeof(cpuset));
+	ret = eal_thread_dump_current_affinity(cpuset, sizeof(cpuset));
 	RTE_LOG(DEBUG, EAL, "lcore %u is ready (tid=%zx;cpuset=[%s%s])\n",
 		lcore_id, (uintptr_t)thread_id, cpuset, ret == 0 ? "" : "...");
 
diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index c3e762c1d9..3aeb5b11ab 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -397,6 +397,8 @@ EXPERIMENTAL {
 	# added in 20.08
 	rte_lcore_callback_register;
 	rte_lcore_callback_unregister;
+	rte_lcore_dump;
+	rte_lcore_iterate;
 	rte_thread_register;
 	rte_thread_unregister;
 };
-- 
2.23.0