A simple array based FIFO of pointers. Intended for net stack so uses
skbs for type safety, but we can replace with with void * if others find
it useful outside of net stack.
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
include/linux/skb_array.h | 127 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 127 insertions(+)
create mode 100644 include/linux/skb_array.h
diff --git a/include/linux/skb_array.h b/include/linux/skb_array.h
new file mode 100644
index 0000000..d2535ad
--- /dev/null
+++ b/include/linux/skb_array.h
@@ -0,0 +1,127 @@
+/*
+ * Author:
+ * Michael S. Tsirkin <m...@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This is a limited-size FIFO maintaining sk_buff structures in FIFO
+ * order, with one CPU producing entries and another consuming entries
+ * from a FIFO.
+ *
+ * This implementation tries to minimize cache-contention when there is a
+ * single producer and a single consumer CPU.
+ */
+
+#ifndef _LINUX_SKB_ARRAY_H
+#define _LINUX_SKB_ARRAY_H 1
+
+#ifdef __KERNEL__
+#include <linux/spinlock.h>
+#include <linux/cache.h>
+#include <linux/types.h>
+#include <linux/compiler.h>
+#include <linux/cache.h>
+#include <linux/slab.h>
+#include <asm/errno.h>
+#endif
+
+struct sk_buff;
+
+struct skb_array {
+ int producer ____cacheline_aligned_in_smp;
+ spinlock_t producer_lock;
+ int consumer ____cacheline_aligned_in_smp;
+ spinlock_t consumer_lock;
+ /* Shared consumer/producer data */
+ int size ____cacheline_aligned_in_smp; /* max entries in queue */
+ struct sk_buff **queue;
+};
+
+/* Note: callers invoking this in a loop must use a compiler barrier,
+ * for example cpu_relax().
+ */
+static inline bool __skb_array_full(struct skb_array *a)
+{
+ return a->queue[a->producer];
+}
+
+/* Note: callers invoking this in a loop must use a compiler barrier,
+ * for example cpu_relax().
+ */
+static inline int __skb_array_produce(struct skb_array *a,
+ struct sk_buff *skb)
+{
+ if (__skb_array_full(a))
+ return -ENOSPC;
+
+ a->queue[a->producer++] = skb;
+ if (unlikely(a->producer >= a->size))
+ a->producer = 0;
+ return 0;
+}
+
+static inline int skb_array_produce_bh(struct skb_array *a,
+ struct sk_buff *skb)
+{
+ int ret;
+
+ spin_lock_bh(&a->producer_lock);
+ ret = __skb_array_produce(a, skb);
+ spin_unlock_bh(&a->producer_lock);
+
+ return ret;
+}
+
+/* Note: callers invoking this in a loop must use a compiler barrier,
+ * for example cpu_relax().
+ */
+static inline struct sk_buff *__skb_array_peek(struct skb_array *a)
+{
+ return a->queue[a->consumer];
+}
+
+/* Must only be called after __skb_array_peek returned !NULL */
+static inline void __skb_array_consume(struct skb_array *a)
+{
+ a->queue[a->consumer++] = NULL;
+ if (unlikely(a->consumer >= a->size))
+ a->consumer = 0;
+}
+
+static inline struct sk_buff *skb_array_consume_bh(struct skb_array *a)
+{
+ struct sk_buff *skb;
+
+ spin_lock_bh(&a->consumer_lock);
+ skb = __skb_array_peek(a);
+ if (skb)
+ __skb_array_consume(a);
+ spin_unlock_bh(&a->consumer_lock);
+
+ return skb;
+}
+
+static inline int skb_array_init(struct skb_array *a, int size, gfp_t gfp)
+{
+ a->queue = kzalloc(ALIGN(size * sizeof *(a->queue), SMP_CACHE_BYTES),
+ gfp);
+ if (!a->queue)
+ return -ENOMEM;
+
+ a->size = size;
+ a->producer = a->consumer = 0;
+ spin_lock_init(&a->producer_lock);
+ spin_lock_init(&a->consumer_lock);
+
+ return 0;
+}
+
+static inline void skb_array_cleanup(struct skb_array *a)
+{
+ kfree(a->queue);
+}
+
+#endif /* _LINUX_SKB_ARRAY_H */
--
MST
