From 5f893b2639b21ffe6834b1aebba392c37d2b83f9 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 12 Dec 2014 20:05:10 -0500 Subject: tracing: Move enabling tracepoints to just after rcu_init() Enabling tracepoints at boot up can be very useful. The tracepoint can be initialized right after RCU has been. There's no need to wait for the early_initcall() to be called. That's too late for some things that can use tracepoints for debugging. Move the logic to enable tracepoints out of the initcalls and into init/main.c to right after rcu_init(). This also allows trace_printk() to be used early too. Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1412121539300.16494@nanos Link: http://lkml.kernel.org/r/20141214164104.307127356@goodmis.org Reviewed-by: Paul E. McKenney Suggested-by: Thomas Gleixner Tested-by: Thomas Gleixner Acked-by: Thomas Gleixner Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'kernel/trace/trace.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 4ceb2546c7ef..ec3ca694665f 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6876,6 +6876,13 @@ out: return ret; } +void __init trace_init(void) +{ + tracer_alloc_buffers(); + init_ftrace_syscalls(); + trace_event_init(); +} + __init static int clear_boot_tracer(void) { /* @@ -6895,6 +6902,5 @@ __init static int clear_boot_tracer(void) return 0; } -early_initcall(tracer_alloc_buffers); fs_initcall(tracer_init_debugfs); late_initcall(clear_boot_tracer); -- cgit v1.2.3 From 0daa2302968c13b657118d6ac92471f8fd2f3f28 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 12 Dec 2014 22:27:10 -0500 Subject: 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 Tested-by: Thomas Gleixner Acked-by: Thomas Gleixner Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'kernel/trace/trace.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ec3ca694665f..e890d2d4ec89 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(); -- cgit v1.2.3