tracing: pass around ring buffer instead of tracer

The latency tracers (irqsoff and wakeup) can swap trace buffers
on the fly. If an event is happening and has reserved data on one of
the buffers, and the latency tracer swaps the global buffer with the
max buffer, the result is that the event may commit the data to the
wrong buffer.

This patch changes the API to the trace recording to be recieve the
buffer that was used to reserve a commit. Then this buffer can be passed
in to the commit.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 12 insertions, 6 deletions

diff --git a/kernel/trace/trace_power.c b/kernel/trace/trace_power.c
index a5d5a4f7745b..fe1a00f1445a 100644
--- a/kernel/trace/trace_power.c
+++ b/kernel/trace/trace_power.c
@@ -38,6 +38,7 @@ static void probe_power_end(struct power_trace *it)
 {
         struct ftrace_event_call *call = &event_power;
         struct ring_buffer_event *event;
+        struct ring_buffer *buffer;
         struct trace_power *entry;
         struct trace_array_cpu *data;
         struct trace_array *tr = power_trace;
@@ -45,18 +46,20 @@ static void probe_power_end(struct power_trace *it)
         if (!trace_power_enabled)
                 return;
 
+        buffer = tr->buffer;
+
         preempt_disable();
         it->end = ktime_get();
         data = tr->data[smp_processor_id()];
 
-        event = trace_buffer_lock_reserve(tr, TRACE_POWER,
+        event = trace_buffer_lock_reserve(buffer, TRACE_POWER,
                                           sizeof(*entry), 0, 0);
         if (!event)
                 goto out;
         entry   = ring_buffer_event_data(event);
         entry->state_data = *it;
-        if (!filter_check_discard(call, entry, tr->buffer, event))
-                trace_buffer_unlock_commit(tr, event, 0, 0);
+        if (!filter_check_discard(call, entry, buffer, event))
+                trace_buffer_unlock_commit(buffer, event, 0, 0);
  out:
         preempt_enable();
 }
@@ -66,6 +69,7 @@ static void probe_power_mark(struct power_trace *it, unsigned int type,
 {
         struct ftrace_event_call *call = &event_power;
         struct ring_buffer_event *event;
+        struct ring_buffer *buffer;
         struct trace_power *entry;
         struct trace_array_cpu *data;
         struct trace_array *tr = power_trace;
@@ -73,6 +77,8 @@ static void probe_power_mark(struct power_trace *it, unsigned int type,
         if (!trace_power_enabled)
                 return;
 
+        buffer = tr->buffer;
+
         memset(it, 0, sizeof(struct power_trace));
         it->state = level;
         it->type = type;
@@ -81,14 +87,14 @@ static void probe_power_mark(struct power_trace *it, unsigned int type,
         it->end = it->stamp;
         data = tr->data[smp_processor_id()];
 
-        event = trace_buffer_lock_reserve(tr, TRACE_POWER,
+        event = trace_buffer_lock_reserve(buffer, TRACE_POWER,
                                           sizeof(*entry), 0, 0);
         if (!event)
                 goto out;
         entry   = ring_buffer_event_data(event);
         entry->state_data = *it;
-        if (!filter_check_discard(call, entry, tr->buffer, event))
-                trace_buffer_unlock_commit(tr, event, 0, 0);
+        if (!filter_check_discard(call, entry, buffer, event))
+                trace_buffer_unlock_commit(buffer, event, 0, 0);
  out:
         preempt_enable();
 }