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ftrace: add ftrace_off_permanent

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Impact: add new API to disable all of ftrace on anomalies

It case of a serious anomaly being detected (like something caught by
lockdep) it is a good idea to disable all tracing immediately, without
grabing any locks.

This patch adds ftrace_off_permanent that disables the tracers, function
tracing and ring buffers without a way to enable them again. This should
only be used when something serious has been detected.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2008-11-21 12:59:38 -05:00 • committed by Ingo Molnar
parent e58918ab9d
commit 69bb54ec05
2 changed files with 17 additions and 0 deletions
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2
include/linux/ftrace.h
View file

@ -257,6 +257,7 @@ extern int ftrace_dump_on_oops;
extern void tracing_start(void); extern void tracing_start(void);
extern void tracing_stop(void); extern void tracing_stop(void);
extern void ftrace_off_permanent(void);
extern void extern void
ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3); ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
@ -290,6 +291,7 @@ ftrace_printk(const char *fmt, ...) __attribute__ ((format (printf, 1, 0)));
static inline void tracing_start(void) { } static inline void tracing_start(void) { }
static inline void tracing_stop(void) { } static inline void tracing_stop(void) { }
static inline void ftrace_off_permanent(void) { }
static inline int static inline int
ftrace_printk(const char *fmt, ...) ftrace_printk(const char *fmt, ...)
{ {

15
kernel/trace/trace.c
View file

@ -660,6 +660,21 @@ static void trace_init_cmdlines(void)
static int trace_stop_count; static int trace_stop_count;
static DEFINE_SPINLOCK(tracing_start_lock); static DEFINE_SPINLOCK(tracing_start_lock);
/**
* ftrace_off_permanent - disable all ftrace code permanently
*
* This should only be called when a serious anomally has
* been detected. This will turn off the function tracing,
* ring buffers, and other tracing utilites. It takes no
* locks and can be called from any context.
*/
void ftrace_off_permanent(void)
{
tracing_disabled = 1;
ftrace_stop();
tracing_off_permanent();
}
/** /**
* tracing_start - quick start of the tracer * tracing_start - quick start of the tracer
* *