[for-next][PATCH 3/4] tracing: Add internal ftrace trace_puts() for ftrace to use

[Steven Rostedt]

From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

There's a few places that ftrace uses trace_printk() for internal
use, but this requires context (normal, softirq, irq, NMI) buffers
to keep things lockless. But the trace_puts() does not, as it can
write the string directly into the ring buffer. Make a internal helper
for trace_puts() and have the internal functions use that.

This way the extra context buffers are not used.

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c |    8 ++++----
 kernel/trace/trace.h |   11 +++++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1b9a791..fa740e5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -443,16 +443,16 @@ void tracing_snapshot(void)
 	unsigned long flags;
 
 	if (!tr->allocated_snapshot) {
-		trace_printk("*** SNAPSHOT NOT ALLOCATED ***\n");
-		trace_printk("*** stopping trace here!   ***\n");
+		internal_trace_puts("*** SNAPSHOT NOT ALLOCATED ***\n");
+		internal_trace_puts("*** stopping trace here!   ***\n");
 		tracing_off();
 		return;
 	}
 
 	/* Note, snapshot can not be used when the tracer uses it */
 	if (tracer->use_max_tr) {
-		trace_printk("*** LATENCY TRACER ACTIVE ***\n");
-		trace_printk("*** Can not use snapshot (sorry) ***\n");
+		internal_trace_puts("*** LATENCY TRACER ACTIVE ***\n");
+		internal_trace_puts("*** Can not use snapshot (sorry) ***\n");
 		return;
 	}
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 98dd79d..c729843 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1034,6 +1034,17 @@ extern const char *__stop___trace_bprintk_fmt[];
 void trace_printk_init_buffers(void);
 void trace_printk_start_comm(void);
 
+/*
+ * Normal trace_printk() and friends allocates special buffers
+ * to do the manipulation, as well as saves the print formats
+ * into sections to display. But the trace infrastructure wants
+ * to use these without the added overhead at the price of being
+ * a bit slower (used mainly for warnings, where we don't care
+ * about performance). The internal_trace_puts() is for such
+ * a purpose.
+ */
+#define internal_trace_puts(str) __trace_puts(_THIS_IP_, str, strlen(str))
+
 #undef FTRACE_ENTRY
 #define FTRACE_ENTRY(call, struct_name, id, tstruct, print, filter)	\
 	extern struct ftrace_event_call					\
-- 
1.7.10.4


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