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Date: Tue, 14 Jul 2015 11:48:48 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Cc: Huang Ying <ying.huang@...el.com>, LKML <linux-kernel@...r.kernel.org>, LKP ML <lkp@...org> Subject: Re: [lkp] [torture] 945fa9c631b: BUG: unable to handle kernel NULL pointer dereference at (null) On Tue, 14 Jul 2015 08:38:29 -0700 "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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