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-rw-r--r--kernel/trace/ring_buffer.c68
1 files changed, 56 insertions, 12 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9c31c9f6b93..dbc0f93396a 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -205,6 +205,7 @@ EXPORT_SYMBOL_GPL(tracing_is_on);
#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT 4U
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
@@ -1170,6 +1171,59 @@ static unsigned rb_calculate_event_length(unsigned length)
return length;
}
+static inline void
+rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *tail_page,
+ unsigned long tail, unsigned long length)
+{
+ struct ring_buffer_event *event;
+
+ /*
+ * Only the event that crossed the page boundary
+ * must fill the old tail_page with padding.
+ */
+ if (tail >= BUF_PAGE_SIZE) {
+ local_sub(length, &tail_page->write);
+ return;
+ }
+
+ event = __rb_page_index(tail_page, tail);
+
+ /*
+ * If this event is bigger than the minimum size, then
+ * we need to be careful that we don't subtract the
+ * write counter enough to allow another writer to slip
+ * in on this page.
+ * We put in a discarded commit instead, to make sure
+ * that this space is not used again.
+ *
+ * If we are less than the minimum size, we don't need to
+ * worry about it.
+ */
+ if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
+ /* No room for any events */
+
+ /* Mark the rest of the page with padding */
+ rb_event_set_padding(event);
+
+ /* Set the write back to the previous setting */
+ local_sub(length, &tail_page->write);
+ return;
+ }
+
+ /* Put in a discarded event */
+ event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
+ event->type_len = RINGBUF_TYPE_PADDING;
+ /* time delta must be non zero */
+ event->time_delta = 1;
+ /* Account for this as an entry */
+ local_inc(&tail_page->entries);
+ local_inc(&cpu_buffer->entries);
+
+ /* Set write to end of buffer */
+ length = (tail + length) - BUF_PAGE_SIZE;
+ local_sub(length, &tail_page->write);
+}
static struct ring_buffer_event *
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
@@ -1264,17 +1318,7 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
cpu_buffer->tail_page->page->time_stamp = *ts;
}
- /*
- * The actual tail page has moved forward.
- */
- if (tail < BUF_PAGE_SIZE) {
- /* Mark the rest of the page with padding */
- event = __rb_page_index(tail_page, tail);
- rb_event_set_padding(event);
- }
-
- /* Set the write back to the previous setting */
- local_sub(length, &tail_page->write);
+ rb_reset_tail(cpu_buffer, tail_page, tail, length);
/*
* If this was a commit entry that failed,
@@ -1293,7 +1337,7 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
out_reset:
/* reset write */
- local_sub(length, &tail_page->write);
+ rb_reset_tail(cpu_buffer, tail_page, tail, length);
if (likely(lock_taken))
__raw_spin_unlock(&cpu_buffer->lock);