diff options
Diffstat (limited to 'kernel/trace/ftrace.c')
| -rw-r--r-- | kernel/trace/ftrace.c | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 6c508ff33c62..67708f46baae 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -413,6 +413,17 @@ static int __register_ftrace_function(struct ftrace_ops *ops) return 0; } +static void ftrace_sync(struct work_struct *work) +{ + /* + * This function is just a stub to implement a hard force + * of synchronize_sched(). This requires synchronizing + * tasks even in userspace and idle. + * + * Yes, function tracing is rude. + */ +} + static int __unregister_ftrace_function(struct ftrace_ops *ops) { int ret; @@ -440,8 +451,12 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops) * so there'll be no new users. We must ensure * all current users are done before we free * the control data. + * Note synchronize_sched() is not enough, as we + * use preempt_disable() to do RCU, but the function + * tracer can be called where RCU is not active + * (before user_exit()). */ - synchronize_sched(); + schedule_on_each_cpu(ftrace_sync); control_ops_free(ops); } } else @@ -456,9 +471,13 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops) /* * Dynamic ops may be freed, we must make sure that all * callers are done before leaving this function. + * + * Again, normal synchronize_sched() is not good enough. + * We need to do a hard force of sched synchronization. */ if (ops->flags & FTRACE_OPS_FL_DYNAMIC) - synchronize_sched(); + schedule_on_each_cpu(ftrace_sync); + return 0; } @@ -622,12 +641,18 @@ static int function_stat_show(struct seq_file *m, void *v) if (rec->counter <= 1) stddev = 0; else { - stddev = rec->time_squared - rec->counter * avg * avg; + /* + * Apply Welford's method: + * s^2 = 1 / (n * (n-1)) * (n * \Sum (x_i)^2 - (\Sum x_i)^2) + */ + stddev = rec->counter * rec->time_squared - + rec->time * rec->time; + /* * Divide only 1000 for ns^2 -> us^2 conversion. * trace_print_graph_duration will divide 1000 again. */ - do_div(stddev, (rec->counter - 1) * 1000); + do_div(stddev, rec->counter * (rec->counter - 1) * 1000); } trace_seq_init(&s); @@ -3512,8 +3537,12 @@ EXPORT_SYMBOL_GPL(ftrace_set_global_notrace); static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata; static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata; +/* Used by function selftest to not test if filter is set */ +bool ftrace_filter_param __initdata; + static int __init set_ftrace_notrace(char *str) { + ftrace_filter_param = true; strlcpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE); return 1; } @@ -3521,6 +3550,7 @@ __setup("ftrace_notrace=", set_ftrace_notrace); static int __init set_ftrace_filter(char *str) { + ftrace_filter_param = true; strlcpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE); return 1; } |