diff options
| -rw-r--r-- | kernel/trace/ring_buffer.c | 68 |
1 files changed, 56 insertions, 12 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 9c31c9f6b93f..dbc0f93396aa 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); |