+/*
+ * When encountering empty buffer, flush current sub-buffer if non-empty
+ * and retry (if new data available to read after flush).
+ */
+static
+ssize_t lttng_event_notifier_group_notif_read(struct file *filp, char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct lttng_event_notifier_group *event_notifier_group = filp->private_data;
+ struct channel *chan = event_notifier_group->chan;
+ struct lib_ring_buffer *buf = event_notifier_group->buf;
+ ssize_t read_count = 0, len;
+ size_t read_offset;
+
+ might_sleep();
+ if (!lttng_access_ok(VERIFY_WRITE, user_buf, count))
+ return -EFAULT;
+
+ /* Finish copy of previous record */
+ if (*ppos != 0) {
+ if (read_count < count) {
+ len = chan->iter.len_left;
+ read_offset = *ppos;
+ goto skip_get_next;
+ }
+ }
+
+ while (read_count < count) {
+ size_t copy_len, space_left;
+
+ len = lib_ring_buffer_get_next_record(chan, buf);
+len_test:
+ if (len < 0) {
+ /*
+ * Check if buffer is finalized (end of file).
+ */
+ if (len == -ENODATA) {
+ /* A 0 read_count will tell about end of file */
+ goto nodata;
+ }
+ if (filp->f_flags & O_NONBLOCK) {
+ if (!read_count)
+ read_count = -EAGAIN;
+ goto nodata;
+ } else {
+ int error;
+
+ /*
+ * No data available at the moment, return what
+ * we got.
+ */
+ if (read_count)
+ goto nodata;
+
+ /*
+ * Wait for returned len to be >= 0 or -ENODATA.
+ */
+ error = wait_event_interruptible(
+ event_notifier_group->read_wait,
+ ((len = lib_ring_buffer_get_next_record(
+ chan, buf)), len != -EAGAIN));
+ CHAN_WARN_ON(chan, len == -EBUSY);
+ if (error) {
+ read_count = error;
+ goto nodata;
+ }
+ CHAN_WARN_ON(chan, len < 0 && len != -ENODATA);
+ goto len_test;
+ }
+ }
+ read_offset = buf->iter.read_offset;
+skip_get_next:
+ space_left = count - read_count;
+ if (len <= space_left) {
+ copy_len = len;
+ chan->iter.len_left = 0;
+ *ppos = 0;
+ } else {
+ copy_len = space_left;
+ chan->iter.len_left = len - copy_len;
+ *ppos = read_offset + copy_len;
+ }
+ if (__lib_ring_buffer_copy_to_user(&buf->backend, read_offset,
+ &user_buf[read_count],
+ copy_len)) {
+ /*
+ * Leave the len_left and ppos values at their current
+ * state, as we currently have a valid event to read.
+ */
+ return -EFAULT;
+ }
+ read_count += copy_len;
+ }
+ return read_count;
+
+nodata:
+ *ppos = 0;
+ chan->iter.len_left = 0;
+ return read_count;
+}
+
+/*
+ * If the ring buffer is non empty (even just a partial subbuffer), return that
+ * there is data available. Perform a ring buffer flush if we encounter a
+ * non-empty ring buffer which does not have any consumeable subbuffer available.
+ */
+static
+unsigned int lttng_event_notifier_group_notif_poll(struct file *filp,
+ poll_table *wait)
+{
+ unsigned int mask = 0;
+ struct lttng_event_notifier_group *event_notifier_group = filp->private_data;
+ struct channel *chan = event_notifier_group->chan;
+ struct lib_ring_buffer *buf = event_notifier_group->buf;
+ const struct lib_ring_buffer_config *config = &chan->backend.config;
+ int finalized, disabled;
+ unsigned long consumed, offset;
+
+ if (filp->f_mode & FMODE_READ) {
+ poll_wait_set_exclusive(wait);
+ poll_wait(filp, &event_notifier_group->read_wait, wait);
+
+ finalized = lib_ring_buffer_is_finalized(config, buf);
+ disabled = lib_ring_buffer_channel_is_disabled(chan);
+
+ /*
+ * lib_ring_buffer_is_finalized() contains a smp_rmb() ordering
+ * finalized load before offsets loads.
+ */
+ WARN_ON(atomic_long_read(&buf->active_readers) != 1);
+retry:
+ if (disabled)
+ return POLLERR;
+
+ offset = lib_ring_buffer_get_offset(config, buf);
+ consumed = lib_ring_buffer_get_consumed(config, buf);
+
+ /*
+ * If there is no buffer available to consume.
+ */
+ if (subbuf_trunc(offset, chan) - subbuf_trunc(consumed, chan) == 0) {
+ /*
+ * If there is a non-empty subbuffer, flush and try again.
+ */
+ if (subbuf_offset(offset, chan) != 0) {
+ lib_ring_buffer_switch_remote(buf);
+ goto retry;
+ }
+
+ if (finalized)
+ return POLLHUP;
+ else {
+ /*
+ * The memory barriers
+ * __wait_event()/wake_up_interruptible() take
+ * care of "raw_spin_is_locked" memory ordering.
+ */
+ if (raw_spin_is_locked(&buf->raw_tick_nohz_spinlock))
+ goto retry;
+ else
+ return 0;
+ }
+ } else {
+ if (subbuf_trunc(offset, chan) - subbuf_trunc(consumed, chan)
+ >= chan->backend.buf_size)
+ return POLLPRI | POLLRDBAND;
+ else
+ return POLLIN | POLLRDNORM;
+ }
+ }
+
+ return mask;
+}
+
+/**
+ * lttng_event_notifier_group_notif_open - event_notifier ring buffer open file operation
+ * @inode: opened inode
+ * @file: opened file
+ *
+ * Open implementation. Makes sure only one open instance of a buffer is
+ * done at a given moment.
+ */
+static int lttng_event_notifier_group_notif_open(struct inode *inode, struct file *file)
+{
+ struct lttng_event_notifier_group *event_notifier_group = inode->i_private;
+ struct lib_ring_buffer *buf = event_notifier_group->buf;
+
+ file->private_data = event_notifier_group;
+ return lib_ring_buffer_open(inode, file, buf);
+}
+
+/**
+ * lttng_event_notifier_group_notif_release - event_notifier ring buffer release file operation
+ * @inode: opened inode
+ * @file: opened file
+ *
+ * Release implementation.
+ */
+static int lttng_event_notifier_group_notif_release(struct inode *inode, struct file *file)
+{
+ struct lttng_event_notifier_group *event_notifier_group = file->private_data;
+ struct lib_ring_buffer *buf = event_notifier_group->buf;
+ int ret;
+
+ ret = lib_ring_buffer_release(inode, file, buf);
+ if (ret)
+ return ret;
+ fput(event_notifier_group->file);
+ return 0;
+}
+
projects / lttng-modules.git / commitdiff
