diff options
| -rw-r--r-- | kernel/trace/ring_buffer.c | 37 |
1 files changed, 33 insertions, 4 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 8295650444c5..dc6d563a6d22 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -320,6 +320,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_data); /* Flag when events were overwritten */ #define RB_MISSED_EVENTS (1 << 31) +/* Missed count stored at end */ +#define RB_MISSED_STORED (1 << 30) struct buffer_data_page { u64 time_stamp; /* page time stamp */ @@ -340,6 +342,7 @@ struct buffer_page { local_t write; /* index for next write */ unsigned read; /* index for next read */ local_t entries; /* entries on this page */ + unsigned long real_end; /* real end of data */ struct buffer_data_page *page; /* Actual data page */ }; @@ -1770,6 +1773,13 @@ rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, kmemcheck_annotate_bitfield(event, bitfield); /* + * Save the original length to the meta data. + * This will be used by the reader to add lost event + * counter. + */ + tail_page->real_end = 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 @@ -2888,6 +2898,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) local_set(&cpu_buffer->reader_page->write, 0); local_set(&cpu_buffer->reader_page->entries, 0); local_set(&cpu_buffer->reader_page->page->commit, 0); + cpu_buffer->reader_page->real_end = 0; spin: /* @@ -3728,11 +3739,11 @@ int ring_buffer_read_page(struct ring_buffer *buffer, struct ring_buffer_event *event; struct buffer_data_page *bpage; struct buffer_page *reader; + unsigned long missed_events; unsigned long flags; unsigned int commit; unsigned int read; u64 save_timestamp; - int missed_events = 0; int ret = -1; if (!cpumask_test_cpu(cpu, buffer->cpumask)) @@ -3766,8 +3777,7 @@ int ring_buffer_read_page(struct ring_buffer *buffer, commit = rb_page_commit(reader); /* Check if any events were dropped */ - if (cpu_buffer->lost_events) - missed_events = 1; + missed_events = cpu_buffer->lost_events; /* * If this page has been partially read or @@ -3829,6 +3839,14 @@ int ring_buffer_read_page(struct ring_buffer *buffer, local_set(&reader->entries, 0); reader->read = 0; *data_page = bpage; + + /* + * Use the real_end for the data size, + * This gives us a chance to store the lost events + * on the page. + */ + if (reader->real_end) + local_set(&bpage->commit, reader->real_end); } ret = read; @@ -3836,8 +3854,19 @@ int ring_buffer_read_page(struct ring_buffer *buffer, /* * Set a flag in the commit field if we lost events */ - if (missed_events) + if (missed_events) { + commit = local_read(&bpage->commit); + + /* If there is room at the end of the page to save the + * missed events, then record it there. + */ + if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) { + memcpy(&bpage->data[commit], &missed_events, + sizeof(missed_events)); + local_add(RB_MISSED_STORED, &bpage->commit); + } local_add(RB_MISSED_EVENTS, &bpage->commit); + } out_unlock: spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |