[dpdk-dev] [PATCH 1/3] mem: provide thread-unsafe contig walk variant

[Anatoly Burakov <anatoly.burakov@intel.com>]

Sometimes, user code needs to walk memseg list while being inside
a memory-related callback. Rather than making everyone copy around
the same iteration code and depending on DPDK internals, provide an
official way to do memseg_contig_walk() inside callbacks.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/common/eal_common_memory.c  | 28 ++++++++++++----------
 lib/librte_eal/common/include/rte_memory.h | 18 ++++++++++++++
 lib/librte_eal/rte_eal_version.map         |  1 +
 3 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index 4f0688f9d..e3320a746 100644
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -788,14 +788,11 @@ rte_mem_lock_page(const void *virt)
 }
 
 int __rte_experimental
-rte_memseg_contig_walk(rte_memseg_contig_walk_t func, void *arg)
+rte_memseg_contig_walk_thread_unsafe(rte_memseg_contig_walk_t func, void *arg)
 {
 	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
 	int i, ms_idx, ret = 0;
 
-	/* do not allow allocations/frees/init while we iterate */
-	rte_rwlock_read_lock(&mcfg->memory_hotplug_lock);
-
 	for (i = 0; i < RTE_MAX_MEMSEG_LISTS; i++) {
 		struct rte_memseg_list *msl = &mcfg->memsegs[i];
 		const struct rte_memseg *ms;
@@ -820,19 +817,26 @@ rte_memseg_contig_walk(rte_memseg_contig_walk_t func, void *arg)
 			len = n_segs * msl->page_sz;
 
 			ret = func(msl, ms, len, arg);
-			if (ret < 0) {
-				ret = -1;
-				goto out;
-			} else if (ret > 0) {
-				ret = 1;
-				goto out;
-			}
+			if (ret)
+				return ret;
 			ms_idx = rte_fbarray_find_next_used(arr,
 					ms_idx + n_segs);
 		}
 	}
-out:
+	return 0;
+}
+
+int __rte_experimental
+rte_memseg_contig_walk(rte_memseg_contig_walk_t func, void *arg)
+{
+	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
+	int ret = 0;
+
+	/* do not allow allocations/frees/init while we iterate */
+	rte_rwlock_read_lock(&mcfg->memory_hotplug_lock);
+	ret = rte_memseg_contig_walk_thread_unsafe(func, arg);
 	rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
+
 	return ret;
 }
 
diff --git a/lib/librte_eal/common/include/rte_memory.h b/lib/librte_eal/common/include/rte_memory.h
index aab9f6fe5..aeba38bfa 100644
--- a/lib/librte_eal/common/include/rte_memory.h
+++ b/lib/librte_eal/common/include/rte_memory.h
@@ -263,6 +263,24 @@ rte_memseg_contig_walk(rte_memseg_contig_walk_t func, void *arg);
 int __rte_experimental
 rte_memseg_list_walk(rte_memseg_list_walk_t func, void *arg);
 
+/**
+ * Walk each VA-contiguous area without performing any locking.
+ *
+ * @note This function does not perform any locking, and is only safe to call
+ *       from within memory-related callback functions.
+ *
+ * @param func
+ *   Iterator function
+ * @param arg
+ *   Argument passed to iterator
+ * @return
+ *   0 if walked over the entire list
+ *   1 if stopped by the user
+ *   -1 if user function reported error
+ */
+int __rte_experimental
+rte_memseg_contig_walk_thread_unsafe(rte_memseg_contig_walk_t func, void *arg);
+
 /**
  * Dump the physical memory layout to a file.
  *
diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index f7dd0e7bc..98bfbe796 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -286,6 +286,7 @@ EXPERIMENTAL {
 	rte_mem_virt2memseg;
 	rte_mem_virt2memseg_list;
 	rte_memseg_contig_walk;
+	rte_memseg_contig_walk_thread_unsafe;
 	rte_memseg_list_walk;
 	rte_memseg_walk;
 	rte_mp_action_register;
-- 
2.17.1