printk/tracing: Add console output tracing

Add a printk.console trace point to record any printk
messages into the trace, regardless of the current
console loglevel. This can help correlate (existing)
printk debugging with other tracing.

Link: http://lkml.kernel.org/r/1322161388.5366.54.camel@jlt3.sipsolutions.net

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 13c0a1143f49..cb8a6bd697c6 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -44,6 +44,9 @@
 
 #include <asm/uaccess.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/printk.h>
+
 /*
  * Architectures can override it:
  */
@@ -542,6 +545,8 @@ MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
 static void _call_console_drivers(unsigned start,
                                 unsigned end, int msg_log_level)
 {
+        trace_console(&LOG_BUF(0), start, end, log_buf_len);
+
         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
                         console_drivers && start != end) {
                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {