Messages in this thread | | | Date | Mon, 14 Dec 2015 11:12:31 -0800 | Subject | Re: [PATCH v3] tracing: Fix rcu splat from idle CPU on boot. | From | Philipp Schrader <> |
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On Mon, Dec 14, 2015 at 11:07 AM, Philipp Schrader <philipp@peloton-tech.com> wrote: > With PREEMPT_RT and most of the lockdep-related options enabled I > encountered this splat when booting our DRA7 evaluation module: > > [ 0.055073] > [ 0.055076] =============================== > [ 0.055079] [ INFO: suspicious RCU usage. ] > [ 0.055084] 4.1.6+ #2 Not tainted > [ 0.055086] ------------------------------- > [ 0.055090] include/trace/events/hist.h:31 suspicious > rcu_dereference_check() usage! > [ 0.055093] > [ 0.055093] other info that might help us debug this: > [ 0.055093] > [ 0.055097] > [ 0.055097] RCU used illegally from idle CPU! > [ 0.055097] rcu_scheduler_active = 1, debug_locks = 1 > [ 0.055100] RCU used illegally from extended quiescent state! > [ 0.055104] no locks held by swapper/0/0. > [ 0.055106] > [ 0.055106] stack backtrace: > [ 0.055112] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.1.6+ #2 > [ 0.055116] Hardware name: Generic DRA74X (Flattened Device Tree) > [ 0.055130] [<c00196b8>] (unwind_backtrace) from [<c001515c>] > (show_stack+0x20/0x24) > [ 0.055146] [<c001515c>] (show_stack) from [<c07bc408>] > (dump_stack+0x84/0xa0) > [ 0.055160] [<c07bc408>] (dump_stack) from [<c009bc38>] > (lockdep_rcu_suspicious+0xb0/0x110) > [ 0.055172] [<c009bc38>] (lockdep_rcu_suspicious) from [<c01246c4>] > (time_hardirqs_off+0x2b8/0x3c8) > [ 0.055184] [<c01246c4>] (time_hardirqs_off) from [<c009a218>] > (trace_hardirqs_off_caller+0x2c/0xf4) > [ 0.055194] [<c009a218>] (trace_hardirqs_off_caller) from > [<c009a2f4>] (trace_hardirqs_off+0x14/0x18) > [ 0.055204] [<c009a2f4>] (trace_hardirqs_off) from [<c00c7ecc>] > (rcu_idle_enter+0x78/0xcc) > [ 0.055213] [<c00c7ecc>] (rcu_idle_enter) from [<c0093eb0>] > (cpu_startup_entry+0x190/0x518) > [ 0.055222] [<c0093eb0>] (cpu_startup_entry) from [<c07b95b4>] > (rest_init+0x13c/0x17c) > [ 0.055231] [<c07b95b4>] (rest_init) from [<c0b32c74>] > (start_kernel+0x320/0x380) > [ 0.055238] [<c0b32c74>] (start_kernel) from [<8000807c>] (0x8000807c) > > As per Steve Rotstedt's suggestion I changed the trace_* calls to > trace_*_rcuidle calls. He pointed out that the trace points were getting > triggered when rcu wasn't watching. > > Signed-off-by: Philipp Schrader <philipp@peloton-tech.com> > Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > kernel/trace/trace_irqsoff.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c > index aaade2e..d0e1d0e 100644 > --- a/kernel/trace/trace_irqsoff.c > +++ b/kernel/trace/trace_irqsoff.c > @@ -450,7 +450,7 @@ EXPORT_SYMBOL_GPL(stop_critical_timings); > #ifdef CONFIG_PROVE_LOCKING > void time_hardirqs_on(unsigned long a0, unsigned long a1) > { > - trace_preemptirqsoff_hist(IRQS_ON, 0); > + trace_preemptirqsoff_hist_rcuidle(IRQS_ON, 0); > if (!preempt_trace() && irq_trace()) > stop_critical_timing(a0, a1); > } > @@ -459,7 +459,7 @@ void time_hardirqs_off(unsigned long a0, unsigned long a1) > { > if (!preempt_trace() && irq_trace()) > start_critical_timing(a0, a1); > - trace_preemptirqsoff_hist(IRQS_OFF, 1); > + trace_preemptirqsoff_hist_rcuidle(IRQS_OFF, 1); > } > > #else /* !CONFIG_PROVE_LOCKING */ > -- > 2.1.4 >
Including Paul E. McKenney and Sebastian Andrzej Siewior.
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