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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2014-12-12 22:27:10 -0500
committerSteven Rostedt <rostedt@goodmis.org>2014-12-15 10:17:38 -0500
commit0daa2302968c13b657118d6ac92471f8fd2f3f28 (patch)
tree8bea68f7bbeab6521c11c01f55b5660082eeedf6 /kernel/trace/trace.c
parent5f893b2639b21ffe6834b1aebba392c37d2b83f9 (diff)
downloadop-kernel-dev-0daa2302968c13b657118d6ac92471f8fd2f3f28.zip
op-kernel-dev-0daa2302968c13b657118d6ac92471f8fd2f3f28.tar.gz
tracing: Add tp_printk cmdline to have tracepoints go to printk()
Add the kernel command line tp_printk option that will have tracepoints that are active sent to printk() as well as to the trace buffer. Passing "tp_printk" will activate this. To turn it off, the sysctl /proc/sys/kernel/tracepoint_printk can have '0' echoed into it. Note, this only works if the cmdline option is used. Echoing 1 into the sysctl file without the cmdline option will have no affect. Note, this is a dangerous option. Having high frequency tracepoints send their data to printk() can possibly cause a live lock. This is another reason why this is only active if the command line option is used. Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1412121539300.16494@nanos Suggested-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace.c')
-rw-r--r--kernel/trace/trace.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ec3ca69..e890d2d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -63,6 +63,10 @@ static bool __read_mostly tracing_selftest_running;
*/
bool __read_mostly tracing_selftest_disabled;
+/* Pipe tracepoints to printk */
+struct trace_iterator *tracepoint_print_iter;
+int tracepoint_printk;
+
/* For tracers that don't implement custom flags */
static struct tracer_opt dummy_tracer_opt[] = {
{ }
@@ -193,6 +197,13 @@ static int __init set_trace_boot_clock(char *str)
}
__setup("trace_clock=", set_trace_boot_clock);
+static int __init set_tracepoint_printk(char *str)
+{
+ if ((strcmp(str, "=0") != 0 && strcmp(str, "=off") != 0))
+ tracepoint_printk = 1;
+ return 1;
+}
+__setup("tp_printk", set_tracepoint_printk);
unsigned long long ns2usecs(cycle_t nsec)
{
@@ -6878,6 +6889,12 @@ out:
void __init trace_init(void)
{
+ if (tracepoint_printk) {
+ tracepoint_print_iter =
+ kmalloc(sizeof(*tracepoint_print_iter), GFP_KERNEL);
+ if (WARN_ON(!tracepoint_print_iter))
+ tracepoint_printk = 0;
+ }
tracer_alloc_buffers();
init_ftrace_syscalls();
trace_event_init();
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