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| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2014-12-12 22:27:10 -0500 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2014-12-15 10:17:38 -0500 |
| commit | 0daa2302968c13b657118d6ac92471f8fd2f3f28 (patch) | |
| tree | 8bea68f7bbeab6521c11c01f55b5660082eeedf6 /kernel/trace/trace.c | |
| parent | 5f893b2639b21ffe6834b1aebba392c37d2b83f9 (diff) | |
| download | linux-stable-0daa2302968c13b657118d6ac92471f8fd2f3f28.tar.gz linux-stable-0daa2302968c13b657118d6ac92471f8fd2f3f28.tar.bz2 linux-stable-0daa2302968c13b657118d6ac92471f8fd2f3f28.zip | |
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.c | 17 |
1 files changed, 17 insertions, 0 deletions
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(); |