On Tue, Oct 20, 2015 at 05:32:28PM -0400, Steven Rostedt wrote: > On Tue, 20 Oct 2015 13:25:28 -0700 > "Paul E. McKenney" <[email protected]> wrote: > > > On Tue, Oct 20, 2015 at 12:10:31PM -0400, Steven Rostedt wrote: > > > > > > Paul, > > > > > > I've spent a couple of days debugging this, and finally found that my > > > stack tracer was calling the stack trace code, which calls > > > __module_address() which asserts the below. > > > > > > Is just calling rcu_irq_enter() and rcu_irq_exit() safe to do > > > everywhere (with interrupts always disabled)? This patch appears to fix > > > the bug. > > > > Yep! Just don't call it from an NMI handler. And don't call it with > > interrupts enabled. The patch looks to have interrupts always disabled, > > and the surrounding code doesn't look like NMI-safe code anyway, so > > should be OK. > > > > Thanx, Paul > > > > Hmm, good point about NMI handler. Right now I think the only thing > protecting this from getting in the critical section while in NMI is > the check that we are using the task struct stack. But that may not be > enough in 32 bit. > > I should probably add a "if (in_nmi()) return" somewhere.
But if there's an arch that doesn't use a separate NMI stack, the NMI might cause the largest stack, which would then remain invisible from the stack-tracer. Should we not instead fix the NMI-safety of this tracer? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
