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, 8 insertions, 4 deletions

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 8631393..19bfc75 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -130,6 +130,7 @@ struct tracer boot_tracer __read_mostly =
 void trace_boot_call(struct boot_trace_call *bt, initcall_t fn)
 {
 	struct ring_buffer_event *event;
+	struct ring_buffer *buffer;
 	struct trace_boot_call *entry;
 	struct trace_array *tr = boot_trace;
 
@@ -142,13 +143,14 @@ void trace_boot_call(struct boot_trace_call *bt, initcall_t fn)
 	sprint_symbol(bt->func, (unsigned long)fn);
 	preempt_disable();
 
-	event = trace_buffer_lock_reserve(tr, TRACE_BOOT_CALL,
+	buffer = tr->buffer;
+	event = trace_buffer_lock_reserve(buffer, TRACE_BOOT_CALL,
 					  sizeof(*entry), 0, 0);
 	if (!event)
 		goto out;
 	entry	= ring_buffer_event_data(event);
 	entry->boot_call = *bt;
-	trace_buffer_unlock_commit(tr, event, 0, 0);
+	trace_buffer_unlock_commit(buffer, event, 0, 0);
  out:
 	preempt_enable();
 }
@@ -156,6 +158,7 @@ void trace_boot_call(struct boot_trace_call *bt, initcall_t fn)
 void trace_boot_ret(struct boot_trace_ret *bt, initcall_t fn)
 {
 	struct ring_buffer_event *event;
+	struct ring_buffer *buffer;
 	struct trace_boot_ret *entry;
 	struct trace_array *tr = boot_trace;
 
@@ -165,13 +168,14 @@ void trace_boot_ret(struct boot_trace_ret *bt, initcall_t fn)
 	sprint_symbol(bt->func, (unsigned long)fn);
 	preempt_disable();
 
-	event = trace_buffer_lock_reserve(tr, TRACE_BOOT_RET,
+	buffer = tr->buffer;
+	event = trace_buffer_lock_reserve(buffer, TRACE_BOOT_RET,
 					  sizeof(*entry), 0, 0);
 	if (!event)
 		goto out;
 	entry	= ring_buffer_event_data(event);
 	entry->boot_ret = *bt;
-	trace_buffer_unlock_commit(tr, event, 0, 0);
+	trace_buffer_unlock_commit(buffer, event, 0, 0);
  out:
 	preempt_enable();
 }