On Tue, 14 Jul 2015 08:38:29 -0700
"Paul E. McKenney" <[email protected]> wrote:
> On Tue, Jul 14, 2015 at 09:04:08PM +0800, Huang Ying wrote:
> > FYI, we noticed the below changes on
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > commit 945fa9c631b04febe295a3a2a00c7e4a3cfb97db ("torture: Dump ftrace
> > buffer when the RCU grace period stalls")
> >
> > We think the commit may reveal a existing bug.
>
> Hmmm... Is this perhaps a very slow boot due to diagnostics? If so,
> might the ftrace buffer not yet be initialized? CCing Steven Rostedt
> for his thoughts.
Is this reproducible?
Does the following patch fix it for you?
-- Steve
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6e79408674aa..4d68dc121687 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6968,6 +6968,9 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
unsigned long flags;
int cnt = 0, cpu;
+ if (tracing_disabled)
+ return;
+
/* Only allow one dump user at a time. */
if (atomic_inc_return(&dump_running) != 1) {
atomic_dec(&dump_running);
--
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