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tracing: Add trace_options kernel command line parameter 

Add trace_options to the kernel command line parameter to be able to
set options at early boot. For example, to enable stack dumps of
events, add the following:

  trace_options=stacktrace

This along with the trace_event option, you can get not only
traces of the events but also the stack dumps with them.

Requested-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2012-11-01 22:56:07 -04:00 committed by Steven Rostedt
parent 0d5c6e1c19
commit 7bcfaf54f5
2 changed files with 55 additions and 15 deletions
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16
Documentation/kernel-parameters.txt
View File

@ -2859,6 +2859,22 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
to facilitate early boot debugging.
See also Documentation/trace/events.txt
trace_options=[option-list]
[FTRACE] Enable or disable tracer options at boot.
The option-list is a comma delimited list of options
that can be enabled or disabled just as if you were
to echo the option name into
/sys/kernel/debug/tracing/trace_options
For example, to enable stacktrace option (to dump the
stack trace of each event), add to the command line:
trace_options=stacktrace
See also Documentation/trace/ftrace.txt "trace options"
section.
transparent_hugepage=
[KNL]
Format: [always|madvise|never]

54
kernel/trace/trace.c
View File

@ -155,6 +155,18 @@ static int __init set_ftrace_dump_on_oops(char *str)
}
__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
static char *trace_boot_options __initdata;
static int __init set_trace_boot_options(char *str)
{
strncpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
trace_boot_options = trace_boot_options_buf;
return 0;
}
__setup("trace_options=", set_trace_boot_options);
unsigned long long ns2usecs(cycle_t nsec)
{
nsec += 500;
@ -2838,24 +2850,14 @@ static void set_tracer_flags(unsigned int mask, int enabled)
trace_printk_start_stop_comm(enabled);
}
static ssize_t
tracing_trace_options_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
static int trace_set_options(char *option)
{
char buf[64];
char *cmp;
int neg = 0;
int ret;
int ret = 0;
int i;
if (cnt >= sizeof(buf))
return -EINVAL;
if (copy_from_user(&buf, ubuf, cnt))
return -EFAULT;
buf[cnt] = 0;
cmp = strstrip(buf);
cmp = strstrip(option);
if (strncmp(cmp, "no", 2) == 0) {
neg = 1;
@ -2874,10 +2876,25 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
mutex_lock(&trace_types_lock);
ret = set_tracer_option(current_trace, cmp, neg);
mutex_unlock(&trace_types_lock);
if (ret)
return ret;
}
return ret;
}
static ssize_t
tracing_trace_options_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
char buf[64];
if (cnt >= sizeof(buf))
return -EINVAL;
if (copy_from_user(&buf, ubuf, cnt))
return -EFAULT;
trace_set_options(buf);
*ppos += cnt;
return cnt;
@ -5133,6 +5150,13 @@ __init static int tracer_alloc_buffers(void)
register_die_notifier(&trace_die_notifier);
while (trace_boot_options) {
char *option;
option = strsep(&trace_boot_options, ",");
trace_set_options(option);
}
return 0;
out_free_cpumask: