Messages in this thread | | | Date | Mon, 7 Nov 2016 12:35:42 -0800 | From | Alexei Starovoitov <> | Subject | Re: ftrace module init race/bug |
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On Mon, Nov 07, 2016 at 03:08:41PM -0500, Steven Rostedt wrote: > On Mon, 7 Nov 2016 11:46:24 -0800 > Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > > Hi Steven, > > > > I'm debugging the following spew: > > > > [ 7139.111213] WARNING: CPU: 8 PID: 856649 at kernel/trace/ftrace.c:2747 ftrace_shutdown+0x263/0x270 > > What kernel version is this, as that line number doesn't line up to > nay warning on 4.9 on 4.9-rc1.
it's our 4.6 with backports. It's line 2766 in 4.9 and as far as I can tell the ftrace logic is the same, so pretty sure it's applicable, but... no reproducer available. Only this spew.
> > do you think the following diff is enough to silence the warning > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > index b1870fbd2b67..edb00bf70d84 100644 > > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -2744,7 +2744,7 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int command) > > struct dyn_ftrace *rec; > > > > do_for_each_ftrace_rec(pg, rec) { > > - if (FTRACE_WARN_ON_ONCE(rec->flags)) > > + if (FTRACE_WARN_ON_ONCE(rec->flags & ~FTRACE_FL_DISABLED)) > > pr_warn(" %pS flags:%lx\n", > > (void *)rec->ip, rec->flags); > > } while_for_each_ftrace_rec(); > > > > or it's a tip of an iceberg and less hacky fix is needed? > > Actually, this may be correct. I need to audit the other > do_for_each_ftrace_rec() loops.
yep, the __ftrace_hash_rec_update() has !FTRACE_FL_DISABLED check, so I thought ftrace_shutdown() may need it too. Should I send the above patch with proper sob?
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