summaryrefslogtreecommitdiff
path: root/include/linux/ptr_ring.h
diff options
context:
space:
mode:
authorMichael S. Tsirkin <mst@redhat.com>2017-05-17 12:14:37 +0800
committerDavid S. Miller <davem@davemloft.net>2017-05-18 10:07:39 -0400
commit197a5212c3dd70be267b5cd930be0fb68bb53018 (patch)
treec02cc773a624a138d29e7b0ae1f27ce47cbb8865 /include/linux/ptr_ring.h
parent1fc4d180b3c6bed0e7f5160bcd553aec89594962 (diff)
ptr_ring: add ptr_ring_unconsume
Applications that consume a batch of entries in one go can benefit from ability to return some of them back into the ring. Add an API for that - assuming there's space. If there's no space naturally can't do this and have to drop entries, but this implies ring is full so we'd likely drop some anyway. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/ptr_ring.h')
-rw-r--r--include/linux/ptr_ring.h55
1 files changed, 55 insertions, 0 deletions
diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 6b2e0dd88569..796b90f6d4e9 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -403,6 +403,61 @@ static inline int ptr_ring_init(struct ptr_ring *r, int size, gfp_t gfp)
return 0;
}
+/*
+ * Return entries into ring. Destroy entries that don't fit.
+ *
+ * Note: this is expected to be a rare slow path operation.
+ *
+ * Note: producer lock is nested within consumer lock, so if you
+ * resize you must make sure all uses nest correctly.
+ * In particular if you consume ring in interrupt or BH context, you must
+ * disable interrupts/BH when doing so.
+ */
+static inline void ptr_ring_unconsume(struct ptr_ring *r, void **batch, int n,
+ void (*destroy)(void *))
+{
+ unsigned long flags;
+ int head;
+
+ spin_lock_irqsave(&r->consumer_lock, flags);
+ spin_lock(&r->producer_lock);
+
+ if (!r->size)
+ goto done;
+
+ /*
+ * Clean out buffered entries (for simplicity). This way following code
+ * can test entries for NULL and if not assume they are valid.
+ */
+ head = r->consumer_head - 1;
+ while (likely(head >= r->consumer_tail))
+ r->queue[head--] = NULL;
+ r->consumer_tail = r->consumer_head;
+
+ /*
+ * Go over entries in batch, start moving head back and copy entries.
+ * Stop when we run into previously unconsumed entries.
+ */
+ while (n) {
+ head = r->consumer_head - 1;
+ if (head < 0)
+ head = r->size - 1;
+ if (r->queue[head]) {
+ /* This batch entry will have to be destroyed. */
+ goto done;
+ }
+ r->queue[head] = batch[--n];
+ r->consumer_tail = r->consumer_head = head;
+ }
+
+done:
+ /* Destroy all entries left in the batch. */
+ while (n)
+ destroy(batch[--n]);
+ spin_unlock(&r->producer_lock);
+ spin_unlock_irqrestore(&r->consumer_lock, flags);
+}
+
static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void **queue,
int size, gfp_t gfp,
void (*destroy)(void *))