Add a bounded queue implementation.

Summary:
- This queue will be used to hold the set of directory crawl / file
migrate operations in the multi-threaded rebalance.
- This is a port of D3712047 to 3.8

Test Plan: Unit test included.

Reviewed By: sshreyas

Change-Id: I25497a64beba744430807b3512eaee5d90f089c4
Reviewed-on: https://review.gluster.org/18197
Reviewed-by: Shreyas Siravara <sshreyas@fb.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/libglusterfs/src/bounded-queue.h b/libglusterfs/src/bounded-queue.h
new file mode 100644
index 00000000000..9de62ab5447
--- /dev/null
+++ b/libglusterfs/src/bounded-queue.h
@@ -0,0 +1,32 @@
+#pragma once
+
+#include <stdint.h>
+#include <pthread.h>
+
+struct queue_entry {
+        struct queue_entry *next;
+};
+
+/// @brief a FIFO queue that holds a limited number of elements.
+///
+/// The queue is blocking, i.e. any attempt to push to a full
+/// queue or read from an empty one will block indefinitely.
+///
+/// When tearing down the queue, blocked processes may be
+/// unblocked by calling bounded_queue_kill(), which will
+/// cause all blocked processes to return with error status.
+struct bounded_queue {
+        struct queue_entry *head;
+        struct queue_entry *tail;
+        uint32_t count;
+        uint32_t limit;
+        int killed;
+        pthread_mutex_t mutex;
+        pthread_cond_t cond;
+};
+
+int bounded_queue_init (struct bounded_queue *q, uint32_t limit);
+int bounded_queue_push (struct bounded_queue *q, struct queue_entry *e);
+struct queue_entry *bounded_queue_pop (struct bounded_queue *q);
+int bounded_queue_kill (struct bounded_queue *q);
+