Fix metadata buffer wait/wakeup

[lttng-modules.git] / lib / ringbuffer / ring_buffer_frontend.c

diff --git a/lib/ringbuffer/ring_buffer_frontend.c b/lib/ringbuffer/ring_buffer_frontend.c
index ecc72ab84f7e3143f930e77cac0bc6ad3de16a8e..6a4c241e84677e3f14f14aee282d0a00a418830a 100644 (file)
--- a/lib/ringbuffer/ring_buffer_frontend.c
+++ b/lib/ringbuffer/ring_buffer_frontend.c
@@ -164,7 +164,6 @@ int lib_ring_buffer_create(struct lib_ring_buffer *buf,
        const struct lib_ring_buffer_config *config = chanb->config;
        struct channel *chan = container_of(chanb, struct channel, backend);
        void *priv = chanb->priv;
-       unsigned int num_subbuf;
        size_t subbuf_header_size;
        u64 tsc;
        int ret;
@@ -203,8 +202,8 @@ int lib_ring_buffer_create(struct lib_ring_buffer *buf,
                goto free_commit;
        }
 
-       num_subbuf = chan->backend.num_subbuf;
        init_waitqueue_head(&buf->read_wait);
+       init_waitqueue_head(&buf->write_wait);
        raw_spin_lock_init(&buf->raw_tick_nohz_spinlock);
 
        /*
@@ -700,11 +699,11 @@ void channel_release(struct kref *kref)
  * @chan: channel to destroy
  *
  * Holds cpu hotplug.
- * Call "destroy" callback, finalize channels, wait for readers to release their
- * reference, then destroy ring buffer data. Note that when readers have
- * completed data consumption of finalized channels, get_subbuf() will return
- * -ENODATA. They should release their handle at that point.
- * Returns the private data pointer.
+ * Call "destroy" callback, finalize channels, and then decrement the
+ * channel reference count.  Note that when readers have completed data
+ * consumption of finalized channels, get_subbuf() will return -ENODATA.
+ * They should release their handle at that point.  Returns the private
+ * data pointer.
  */
 void *channel_destroy(struct channel *chan)
 {
@@ -869,6 +868,8 @@ EXPORT_SYMBOL_GPL(lib_ring_buffer_snapshot);
 
 /**
  * lib_ring_buffer_put_snapshot - move consumed counter forward
+ *
+ * Should only be called from consumer context.
  * @buf: ring buffer
  * @consumed_new: new consumed count value
  */
@@ -890,6 +891,8 @@ void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
        while ((long) consumed - (long) consumed_new < 0)
                consumed = atomic_long_cmpxchg(&buf->consumed, consumed,
                                               consumed_new);
+       /* Wake-up the metadata producer */
+       wake_up_interruptible(&buf->write_wait);
 }
 EXPORT_SYMBOL_GPL(lib_ring_buffer_move_consumer);