Messages in this thread | | | Date | Thu, 4 Mar 2010 06:18:53 +0100 | From | Frederic Weisbecker <> | Subject | Re: 2.6.33: ftrace triggers soft lockup |
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On Thu, Mar 04, 2010 at 01:10:16PM +0800, Américo Wang wrote: > On Thu, Mar 4, 2010 at 11:18 AM, Steven Rostedt <rostedt@goodmis.org> wrote: > > On Thu, 2010-03-04 at 11:01 +0800, Américo Wang wrote: > > > >> > > >> > So it is stuck in stop machine. I wonder where exactly. I see some do_exit > >> > at the top but I wonder how much they are reliable. > >> > >> Well, I think 'kstop' is just random, sometimes I got 'watchdog' or some other > >> process. > >> > >> > > >> > Anyway, as Steve said, we really need a full config to reproduce it. > >> > > >> > >> Done in another reply. > > > > Thanks! > > > > Frederic, I notice that lockdep is on, did anything change that might > > slow down the code in lockdep, or is the function graph tracer doing > > more locking? > > > > I'm betting that we are hitting a live lock. That is, an interrupt goes > > off, it is being traced, and the function graph is tracing it, but some > > locking is happening (although it also tracks disabling of interrupts) > > and this slows the interrupt handler down enough that when it finishes, > > another interrupt goes off. > > > > Américo, > > > > Could you disable LOCKDEP and see if you still encounter this lockup? > > > > Sure, after disabling LOCKDEP, I can't see the warning, _but_ the system > is still as unacceptablly slow as when LOCKDEP was enabled.
Looks like a progress. It doesn't appear to be a true lockup but more a starvation or a livelock.
I'm building your config, hopefully I could reproduce.
Thanks.
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