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-rw-r--r--drivers/oprofile/cpu_buffer.c4
-rw-r--r--include/linux/ring_buffer.h6
-rw-r--r--kernel/trace/ring_buffer.c72
-rw-r--r--kernel/trace/ring_buffer_benchmark.c2
-rw-r--r--kernel/trace/trace.c4
-rw-r--r--kernel/trace/trace_functions_graph.c5
-rw-r--r--kernel/trace/trace_selftest.c2
7 files changed, 79 insertions, 16 deletions
diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index 166b67ea622f..7581dbe456da 100644
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -186,14 +186,14 @@ int op_cpu_buffer_write_commit(struct op_entry *entry)
struct op_sample *op_cpu_buffer_read_entry(struct op_entry *entry, int cpu)
{
struct ring_buffer_event *e;
- e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
+ e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL, NULL);
if (e)
goto event;
if (ring_buffer_swap_cpu(op_ring_buffer_read,
op_ring_buffer_write,
cpu))
return NULL;
- e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
+ e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL, NULL);
if (e)
goto event;
return NULL;
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 5fcc31ed5771..c8297761e414 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -120,9 +120,11 @@ int ring_buffer_write(struct ring_buffer *buffer,
unsigned long length, void *data);
struct ring_buffer_event *
-ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts);
+ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
+ unsigned long *lost_events);
struct ring_buffer_event *
-ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts);
+ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
+ unsigned long *lost_events);
struct ring_buffer_iter *
ring_buffer_read_start(struct ring_buffer *buffer, int cpu);
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index d1187ef20caf..8295650444c5 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -318,6 +318,9 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_data);
#define TS_MASK ((1ULL << TS_SHIFT) - 1)
#define TS_DELTA_TEST (~TS_MASK)
+/* Flag when events were overwritten */
+#define RB_MISSED_EVENTS (1 << 31)
+
struct buffer_data_page {
u64 time_stamp; /* page time stamp */
local_t commit; /* write committed index */
@@ -416,6 +419,12 @@ int ring_buffer_print_page_header(struct trace_seq *s)
(unsigned int)sizeof(field.commit),
(unsigned int)is_signed_type(long));
+ ret = trace_seq_printf(s, "\tfield: int overwrite;\t"
+ "offset:%u;\tsize:%u;\tsigned:%u;\n",
+ (unsigned int)offsetof(typeof(field), commit),
+ 1,
+ (unsigned int)is_signed_type(long));
+
ret = trace_seq_printf(s, "\tfield: char data;\t"
"offset:%u;\tsize:%u;\tsigned:%u;\n",
(unsigned int)offsetof(typeof(field), data),
@@ -439,6 +448,8 @@ struct ring_buffer_per_cpu {
struct buffer_page *tail_page; /* write to tail */
struct buffer_page *commit_page; /* committed pages */
struct buffer_page *reader_page;
+ unsigned long lost_events;
+ unsigned long last_overrun;
local_t commit_overrun;
local_t overrun;
local_t entries;
@@ -2835,6 +2846,7 @@ static struct buffer_page *
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *reader = NULL;
+ unsigned long overwrite;
unsigned long flags;
int nr_loops = 0;
int ret;
@@ -2896,6 +2908,18 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
/*
+ * We want to make sure we read the overruns after we set up our
+ * pointers to the next object. The writer side does a
+ * cmpxchg to cross pages which acts as the mb on the writer
+ * side. Note, the reader will constantly fail the swap
+ * while the writer is updating the pointers, so this
+ * guarantees that the overwrite recorded here is the one we
+ * want to compare with the last_overrun.
+ */
+ smp_mb();
+ overwrite = local_read(&(cpu_buffer->overrun));
+
+ /*
* Here's the tricky part.
*
* We need to move the pointer past the header page.
@@ -2926,6 +2950,11 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
cpu_buffer->reader_page = reader;
rb_reset_reader_page(cpu_buffer);
+ if (overwrite != cpu_buffer->last_overrun) {
+ cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
+ cpu_buffer->last_overrun = overwrite;
+ }
+
goto again;
out:
@@ -3002,8 +3031,14 @@ static void rb_advance_iter(struct ring_buffer_iter *iter)
rb_advance_iter(iter);
}
+static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ return cpu_buffer->lost_events;
+}
+
static struct ring_buffer_event *
-rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts)
+rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
+ unsigned long *lost_events)
{
struct ring_buffer_event *event;
struct buffer_page *reader;
@@ -3055,6 +3090,8 @@ rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts)
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
cpu_buffer->cpu, ts);
}
+ if (lost_events)
+ *lost_events = rb_lost_events(cpu_buffer);
return event;
default:
@@ -3165,12 +3202,14 @@ static inline int rb_ok_to_lock(void)
* @buffer: The ring buffer to read
* @cpu: The cpu to peak at
* @ts: The timestamp counter of this event.
+ * @lost_events: a variable to store if events were lost (may be NULL)
*
* This will return the event that will be read next, but does
* not consume the data.
*/
struct ring_buffer_event *
-ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
+ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
+ unsigned long *lost_events)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct ring_buffer_event *event;
@@ -3185,7 +3224,7 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
local_irq_save(flags);
if (dolock)
spin_lock(&cpu_buffer->reader_lock);
- event = rb_buffer_peek(cpu_buffer, ts);
+ event = rb_buffer_peek(cpu_buffer, ts, lost_events);
if (event && event->type_len == RINGBUF_TYPE_PADDING)
rb_advance_reader(cpu_buffer);
if (dolock)
@@ -3227,13 +3266,17 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
/**
* ring_buffer_consume - return an event and consume it
* @buffer: The ring buffer to get the next event from
+ * @cpu: the cpu to read the buffer from
+ * @ts: a variable to store the timestamp (may be NULL)
+ * @lost_events: a variable to store if events were lost (may be NULL)
*
* Returns the next event in the ring buffer, and that event is consumed.
* Meaning, that sequential reads will keep returning a different event,
* and eventually empty the ring buffer if the producer is slower.
*/
struct ring_buffer_event *
-ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
+ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
+ unsigned long *lost_events)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event = NULL;
@@ -3254,9 +3297,11 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
if (dolock)
spin_lock(&cpu_buffer->reader_lock);
- event = rb_buffer_peek(cpu_buffer, ts);
- if (event)
+ event = rb_buffer_peek(cpu_buffer, ts, lost_events);
+ if (event) {
+ cpu_buffer->lost_events = 0;
rb_advance_reader(cpu_buffer);
+ }
if (dolock)
spin_unlock(&cpu_buffer->reader_lock);
@@ -3405,6 +3450,9 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
cpu_buffer->write_stamp = 0;
cpu_buffer->read_stamp = 0;
+ cpu_buffer->lost_events = 0;
+ cpu_buffer->last_overrun = 0;
+
rb_head_page_activate(cpu_buffer);
}
@@ -3684,6 +3732,7 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
unsigned int commit;
unsigned int read;
u64 save_timestamp;
+ int missed_events = 0;
int ret = -1;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
@@ -3716,6 +3765,10 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
read = reader->read;
commit = rb_page_commit(reader);
+ /* Check if any events were dropped */
+ if (cpu_buffer->lost_events)
+ missed_events = 1;
+
/*
* If this page has been partially read or
* if len is not big enough to read the rest of the page or
@@ -3779,6 +3832,13 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
}
ret = read;
+ cpu_buffer->lost_events = 0;
+ /*
+ * Set a flag in the commit field if we lost events
+ */
+ if (missed_events)
+ local_add(RB_MISSED_EVENTS, &bpage->commit);
+
out_unlock:
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index df74c7982255..dc56556b55a2 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -81,7 +81,7 @@ static enum event_status read_event(int cpu)
int *entry;
u64 ts;
- event = ring_buffer_consume(buffer, cpu, &ts);
+ event = ring_buffer_consume(buffer, cpu, &ts, NULL);
if (!event)
return EVENT_DROPPED;
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 3ec2ee6f6560..fabb0033a9be 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1556,7 +1556,7 @@ peek_next_entry(struct trace_iterator *iter, int cpu, u64 *ts)
if (buf_iter)
event = ring_buffer_iter_peek(buf_iter, ts);
else
- event = ring_buffer_peek(iter->tr->buffer, cpu, ts);
+ event = ring_buffer_peek(iter->tr->buffer, cpu, ts, NULL);
ftrace_enable_cpu();
@@ -1635,7 +1635,7 @@ static void trace_consume(struct trace_iterator *iter)
{
/* Don't allow ftrace to trace into the ring buffers */
ftrace_disable_cpu();
- ring_buffer_consume(iter->tr->buffer, iter->cpu, &iter->ts);
+ ring_buffer_consume(iter->tr->buffer, iter->cpu, &iter->ts, NULL);
ftrace_enable_cpu();
}
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index e6989d9b44da..a7f75fb10aa4 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -489,9 +489,10 @@ get_return_for_leaf(struct trace_iterator *iter,
* We need to consume the current entry to see
* the next one.
*/
- ring_buffer_consume(iter->tr->buffer, iter->cpu, NULL);
+ ring_buffer_consume(iter->tr->buffer, iter->cpu,
+ NULL, NULL);
event = ring_buffer_peek(iter->tr->buffer, iter->cpu,
- NULL);
+ NULL, NULL);
}
if (!event)
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 280fea470d67..e50180874c63 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -29,7 +29,7 @@ static int trace_test_buffer_cpu(struct trace_array *tr, int cpu)
struct trace_entry *entry;
unsigned int loops = 0;
- while ((event = ring_buffer_consume(tr->buffer, cpu, NULL))) {
+ while ((event = ring_buffer_consume(tr->buffer, cpu, NULL, NULL))) {
entry = ring_buffer_event_data(event);
/*
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