diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/ring_buffer.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b5ed553e0a45..781ce359976c 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2208,6 +2208,21 @@ static unsigned rb_calculate_event_length(unsigned length) length += RB_EVNT_HDR_SIZE; length = ALIGN(length, RB_ARCH_ALIGNMENT); + /* + * In case the time delta is larger than the 27 bits for it + * in the header, we need to add a timestamp. If another + * event comes in when trying to discard this one to increase + * the length, then the timestamp will be added in the allocated + * space of this event. If length is bigger than the size needed + * for the TIME_EXTEND, then padding has to be used. The events + * length must be either RB_LEN_TIME_EXTEND, or greater than or equal + * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. + * As length is a multiple of 4, we only need to worry if it + * is 12 (RB_LEN_TIME_EXTEND + 4). + */ + if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) + length += RB_ALIGNMENT; + return length; } |