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authorLi Zefan <lizf@cn.fujitsu.com>2010-08-23 04:50:12 -0400
committerSteven Rostedt <rostedt@goodmis.org>2010-08-31 16:46:23 -0400
commit3aaba20f26f58843e8f20611e5c0b1c06954310f (patch)
treead15d7aa21af465ddf6091eb490d84312089f245 /kernel
parentfa66f07aa1f0950e1dc78b7ab39728b3f8aa77a1 (diff)
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: Li Zefan <lizf@cn.fujitsu.com> Cc: stable@kernel.org LKML-Reference: <4C723644.4040708@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/ftrace.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0d88ce9b9fb8..7cb1f45a1de1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -381,12 +381,19 @@ static int function_stat_show(struct seq_file *m, void *v)
381{ 381{
382 struct ftrace_profile *rec = v; 382 struct ftrace_profile *rec = v;
383 char str[KSYM_SYMBOL_LEN]; 383 char str[KSYM_SYMBOL_LEN];
384 int ret = 0;
384#ifdef CONFIG_FUNCTION_GRAPH_TRACER 385#ifdef CONFIG_FUNCTION_GRAPH_TRACER
385 static DEFINE_MUTEX(mutex);
386 static struct trace_seq s; 386 static struct trace_seq s;
387 unsigned long long avg; 387 unsigned long long avg;
388 unsigned long long stddev; 388 unsigned long long stddev;
389#endif 389#endif
390 mutex_lock(&ftrace_profile_lock);
391
392 /* we raced with function_profile_reset() */
393 if (unlikely(rec->counter == 0)) {
394 ret = -EBUSY;
395 goto out;
396 }
390 397
391 kallsyms_lookup(rec->ip, NULL, NULL, NULL, str); 398 kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
392 seq_printf(m, " %-30.30s %10lu", str, rec->counter); 399 seq_printf(m, " %-30.30s %10lu", str, rec->counter);
@@ -408,7 +415,6 @@ static int function_stat_show(struct seq_file *m, void *v)
408 do_div(stddev, (rec->counter - 1) * 1000); 415 do_div(stddev, (rec->counter - 1) * 1000);
409 } 416 }
410 417
411 mutex_lock(&mutex);
412 trace_seq_init(&s); 418 trace_seq_init(&s);
413 trace_print_graph_duration(rec->time, &s); 419 trace_print_graph_duration(rec->time, &s);
414 trace_seq_puts(&s, " "); 420 trace_seq_puts(&s, " ");
@@ -416,11 +422,12 @@ static int function_stat_show(struct seq_file *m, void *v)
416 trace_seq_puts(&s, " "); 422 trace_seq_puts(&s, " ");
417 trace_print_graph_duration(stddev, &s); 423 trace_print_graph_duration(stddev, &s);
418 trace_print_seq(m, &s); 424 trace_print_seq(m, &s);
419 mutex_unlock(&mutex);
420#endif 425#endif
421 seq_putc(m, '\n'); 426 seq_putc(m, '\n');
427out:
428 mutex_unlock(&ftrace_profile_lock);
422 429
423 return 0; 430 return ret;
424} 431}
425 432
426static void ftrace_profile_reset(struct ftrace_profile_stat *stat) 433static void ftrace_profile_reset(struct ftrace_profile_stat *stat)