[PATCH v2 4/5] tracing: Make snapshot trigger affect the correct instance

From: Howard Cochran
Date: Fri Apr 15 2016 - 18:33:21 EST


Currently, the snapshot trigger always snapshots the top level instance,
even if it was triggered within an instance. Fixed by using the trace_array
associated with the trace_event_file which fired the trigger.

Signed-off-by: Howard Cochran <hcochran@xxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 38 ++++++++++++++++++++++---------------
kernel/trace/trace.h | 1 +
kernel/trace/trace_events_trigger.c | 2 +-
3 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c78fe42..e98770b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -620,22 +620,11 @@ EXPORT_SYMBOL_GPL(__trace_bputs);

#ifdef CONFIG_TRACER_SNAPSHOT
/**
- * trace_snapshot - take a snapshot of the current buffer.
- *
- * This causes a swap between the snapshot buffer and the current live
- * tracing buffer. You can use this to take snapshots of the live
- * trace when some condition is triggered, but continue to trace.
- *
- * Note, make sure to allocate the snapshot with either
- * a tracing_snapshot_alloc(), or by doing it manually
- * with: echo 1 > /sys/kernel/debug/tracing/snapshot
- *
- * If the snapshot buffer is not allocated, it will stop tracing.
- * Basically making a permanent snapshot.
+ * trace_snapshot - take a snapshot of a buffer.
+ * @tr: Which tracing buffer (instance) to take a snapshot of
*/
-void tracing_snapshot(void)
+void __tracing_snapshot(struct trace_array *tr)
{
- struct trace_array *tr = &global_trace;
struct tracer *tracer = tr->current_trace;
unsigned long flags;

@@ -648,7 +637,7 @@ void tracing_snapshot(void)
if (!tr->allocated_snapshot) {
internal_trace_puts("*** SNAPSHOT NOT ALLOCATED ***\n");
internal_trace_puts("*** stopping trace here! ***\n");
- tracing_off();
+ tracer_tracing_off(tr);
return;
}

@@ -663,6 +652,25 @@ void tracing_snapshot(void)
update_max_tr(tr, current, smp_processor_id());
local_irq_restore(flags);
}
+
+/**
+ * trace_snapshot - take a snapshot of the top level buffer.
+ *
+ * This causes a swap between the snapshot buffer and the current live
+ * tracing buffer. You can use this to take snapshots of the live
+ * trace when some condition is triggered, but continue to trace.
+ *
+ * Note, make sure to allocate the snapshot with either
+ * a tracing_snapshot_alloc(), or by doing it manually
+ * with: echo 1 > /sys/kernel/debug/tracing/snapshot
+ *
+ * If the snapshot buffer is not allocated, it will stop tracing.
+ * Basically making a permanent snapshot.
+ */
+void tracing_snapshot(void)
+{
+ __tracing_snapshot(&global_trace);
+}
EXPORT_SYMBOL_GPL(tracing_snapshot);

static int resize_buffer_duplicate_size(struct trace_buffer *trace_buf,
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index d3bc0e8..d98d54c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -717,6 +717,7 @@ enum print_line_t print_trace_line(struct trace_iterator *iter);
extern char trace_find_mark(unsigned long long duration);

void __trace_dump_stack(int skip, struct trace_array *tr);
+void __tracing_snapshot(struct trace_array *tr);
int tracer_tracing_is_on(struct trace_array *tr);
void tracer_tracing_on(struct trace_array *tr);
void tracer_tracing_off(struct trace_array *tr);
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 3595688..2f7dc19 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -901,7 +901,7 @@ static void
snapshot_trigger(struct event_trigger_data *data, void *rec,
struct trace_event_file *file)
{
- tracing_snapshot();
+ __tracing_snapshot(file->tr);
}

static void
--
1.9.1