提交 3aaba20f 编写于 作者: L Li Zefan 提交者: Steven Rostedt

tracing: Fix a race in function profile

While we are reading trace_stat/functionX and someone just
disabled function_profile at that time, we can trigger this:

	divide error: 0000 [#1] PREEMPT SMP
	...
	EIP is at function_stat_show+0x90/0x230
	...

This fix just takes the ftrace_profile_lock and checks if
rec->counter is 0. If it's 0, we know the profile buffer
has been reset.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: stable@kernel.org
LKML-Reference: <4C723644.4040708@cn.fujitsu.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
上级 fa66f07a
......@@ -381,12 +381,19 @@ static int function_stat_show(struct seq_file *m, void *v)
{
struct ftrace_profile *rec = v;
char str[KSYM_SYMBOL_LEN];
int ret = 0;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static DEFINE_MUTEX(mutex);
static struct trace_seq s;
unsigned long long avg;
unsigned long long stddev;
#endif
mutex_lock(&ftrace_profile_lock);
/* we raced with function_profile_reset() */
if (unlikely(rec->counter == 0)) {
ret = -EBUSY;
goto out;
}
kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
seq_printf(m, " %-30.30s %10lu", str, rec->counter);
......@@ -408,7 +415,6 @@ static int function_stat_show(struct seq_file *m, void *v)
do_div(stddev, (rec->counter - 1) * 1000);
}
mutex_lock(&mutex);
trace_seq_init(&s);
trace_print_graph_duration(rec->time, &s);
trace_seq_puts(&s, " ");
......@@ -416,11 +422,12 @@ static int function_stat_show(struct seq_file *m, void *v)
trace_seq_puts(&s, " ");
trace_print_graph_duration(stddev, &s);
trace_print_seq(m, &s);
mutex_unlock(&mutex);
#endif
seq_putc(m, '\n');
out:
mutex_unlock(&ftrace_profile_lock);
return 0;
return ret;
}
static void ftrace_profile_reset(struct ftrace_profile_stat *stat)
......
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