From: Francis Deslauriers <francis.deslauriers@efficios.com>
Date: Mon, 24 Aug 2020 21:02:05 +0000 (-0400)
Subject: common: Add index allocator for error counters
X-Git-Tag: v2.13.0-rc1~186
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=246611b0dffa58fbc0e2329ddf6f9dc9d9eff7ce;p=lttng-tools.git

common: Add index allocator for error counters

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I677a8f5b774315eadb8e3b2c2f2a5b1aae02133f
---

diff --git a/src/common/Makefile.am b/src/common/Makefile.am
index caf588e40..a56775e31 100644
--- a/src/common/Makefile.am
+++ b/src/common/Makefile.am
@@ -71,6 +71,7 @@ libcommon_la_SOURCES = \
 	fs-handle.c fs-handle.h fs-handle-internal.h \
 	futex.c futex.h \
 	kernel-probe.c \
+	index-allocator.c index-allocator.h \
 	location.c \
 	log-level-rule.c \
 	mi-lttng.c mi-lttng.h \
diff --git a/src/common/index-allocator.c b/src/common/index-allocator.c
new file mode 100644
index 000000000..3de09a831
--- /dev/null
+++ b/src/common/index-allocator.c
@@ -0,0 +1,128 @@
+/*
+ * Copyright (C) 2020 Francis Deslauriers <francis.deslauriers@efficios.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ */
+
+#include <assert.h>
+#include <inttypes.h>
+
+#include <urcu.h>
+#include <urcu/list.h>
+
+#include "macros.h"
+#include "error.h"
+
+#include "index-allocator.h"
+
+struct lttng_index_allocator {
+	struct cds_list_head unused_list;
+	uint64_t size;
+	uint64_t position;
+};
+
+struct lttng_index {
+	uint64_t index;
+	struct cds_list_head head;
+};
+
+struct lttng_index_allocator *lttng_index_allocator_create(
+		uint64_t index_count)
+{
+	struct lttng_index_allocator *allocator = NULL;
+
+	allocator = zmalloc(sizeof(*allocator));
+	if (!allocator) {
+		PERROR("Failed to allocate index allocator");
+		goto end;
+	}
+
+	allocator->size = index_count;
+	allocator->position = 0;
+
+	CDS_INIT_LIST_HEAD(&allocator->unused_list);
+
+end:
+	return allocator;
+}
+
+uint64_t lttng_index_allocator_get_index_count(struct lttng_index_allocator *allocator)
+{
+	return allocator->size;
+}
+
+enum lttng_index_allocator_status lttng_index_allocator_alloc(
+		struct lttng_index_allocator *allocator,
+		uint64_t *allocated_index)
+{
+	enum lttng_index_allocator_status status =
+			LTTNG_INDEX_ALLOCATOR_STATUS_OK;
+
+	if (cds_list_empty(&allocator->unused_list)) {
+		if (allocator->position >= allocator->size) {
+			/* No indices left. */
+			status = LTTNG_INDEX_ALLOCATOR_STATUS_EMPTY;
+			goto end;
+		}
+
+		*allocated_index = allocator->position++;
+	} else {
+		struct lttng_index *index;
+
+		index = cds_list_first_entry(&allocator->unused_list,
+				typeof(*index), head);
+		cds_list_del(&index->head);
+		*allocated_index = index->index;
+		free(index);
+	}
+
+end:
+	return status;
+}
+
+enum lttng_index_allocator_status lttng_index_allocator_release(
+		struct lttng_index_allocator *allocator, uint64_t idx)
+{
+	struct lttng_index *index = NULL;
+	enum lttng_index_allocator_status status =
+			LTTNG_INDEX_ALLOCATOR_STATUS_OK;
+
+	assert(idx < allocator->size);
+
+	index = zmalloc(sizeof(*index));
+	if (!index) {
+		PERROR("Failed to allocate free index queue");
+		status = LTTNG_INDEX_ALLOCATOR_STATUS_ERROR;
+		goto end;
+	}
+
+	index->index = idx;
+	cds_list_add_tail(&index->head, &allocator->unused_list);
+
+end:
+	return status;
+}
+
+void lttng_index_allocator_destroy(struct lttng_index_allocator *allocator)
+{
+	struct lttng_index *index = NULL, *tmp_index = NULL;
+
+	if (!allocator) {
+		return;
+	}
+
+	if (lttng_index_allocator_get_index_count(allocator) > 0) {
+		WARN("Destroying index allocator with %" PRIu64
+				" slot indexes still in use",
+				lttng_index_allocator_get_index_count(allocator));
+	}
+
+	cds_list_for_each_entry_safe(index, tmp_index,
+			&allocator->unused_list, head) {
+		cds_list_del(&index->head);
+		free(index);
+	}
+
+	free(allocator);
+}
diff --git a/src/common/index-allocator.h b/src/common/index-allocator.h
new file mode 100644
index 000000000..3da733e9e
--- /dev/null
+++ b/src/common/index-allocator.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2020 Francis Deslauriers <francis.deslauriers@efficios.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ */
+
+#ifndef _COMMON_INDEX_ALLOCATOR_H
+#define _COMMON_INDEX_ALLOCATOR_H
+
+#include <inttypes.h>
+
+struct lttng_index_allocator;
+
+enum lttng_index_allocator_status {
+	LTTNG_INDEX_ALLOCATOR_STATUS_OK,
+	LTTNG_INDEX_ALLOCATOR_STATUS_EMPTY,
+	LTTNG_INDEX_ALLOCATOR_STATUS_ERROR,
+};
+
+/*
+ * Create an index allocator of `index_count` slots.
+ */
+struct lttng_index_allocator *lttng_index_allocator_create(
+		uint64_t index_count);
+
+/*
+ * Get the number of indexes currently in use.
+ */
+uint64_t lttng_index_allocator_get_index_count(
+	struct lttng_index_allocator *allocator);
+
+/*
+ * Allocate (i.e. reserve) a slot.
+ */
+enum lttng_index_allocator_status lttng_index_allocator_alloc(
+		struct lttng_index_allocator *allocator,
+		uint64_t *index);
+
+/*
+ * Release a slot by index. The slot will be re-used by the index allocator
+ * in future 'alloc' calls.
+ */
+enum lttng_index_allocator_status lttng_index_allocator_release(
+		struct lttng_index_allocator *allocator, uint64_t index);
+
+/*
+ * Destroy an index allocator.
+ */
+void lttng_index_allocator_destroy(struct lttng_index_allocator *allocator);
+
+#endif /* _COMMON_INDEX_ALLOCATOR_H */