Merge tag 'trace-3.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt...

[cascardo/linux.git] / Documentation / kernel-parameters.txt

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1de8335..bda85f1 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3570,6 +3570,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        See also Documentation/trace/ftrace.txt "trace options"
                        section.
 
+       tp_printk[FTRACE]
+                       Have the tracepoints sent to printk as well as the
+                       tracing ring buffer. This is useful for early boot up
+                       where the system hangs or reboots and does not give the
+                       option for reading the tracing buffer or performing a
+                       ftrace_dump_on_oops.
+
+                       To turn off having tracepoints sent to printk,
+                        echo 0 > /proc/sys/kernel/tracepoint_printk
+                       Note, echoing 1 into this file without the
+                       tracepoint_printk kernel cmdline option has no effect.
+
+                       ** CAUTION **
+
+                       Having tracepoints sent to printk() and activating high
+                       frequency tracepoints such as irq or sched, can cause
+                       the system to live lock.
+
        traceoff_on_warning
                        [FTRACE] enable this option to disable tracing when a
                        warning is hit. This turns off "tracing_on". Tracing can