Messages in this thread | | | Date | Sat, 21 Mar 2009 21:09:19 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 0/5] [GIT PULL] updates for tip/tracing/ftrace |
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> On Sat, Mar 21, 2009 at 01:25:23PM -0400, Steven Rostedt wrote: > > > > > > On Sat, 21 Mar 2009, Ingo Molnar wrote: > > > > > > > > * Ingo Molnar <mingo@elte.hu> wrote: > > > > > > > > > > > * Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > > > > > > > > > On Fri, 20 Mar 2009, Frederic Weisbecker wrote: > > > > > > > > > > > > > > > > VERBOSE_PRINTK_STRING("rcu_torture_reader task started"); > > > > > > > > - set_user_nice(current, 19); > > > > > > > > + set_user_nice(current, -1); > > > > > > > > if (irqreader && cur_ops->irqcapable) > > > > > > > > setup_timer_on_stack(&t, rcu_torture_timer, 0); > > > > > > > > > > > > > > i dont have a reproducer right now. Can you trigger it with latest > > > > > > > -tip, which has this commit included: > > > > > > > > > > > > > > 04cb9ac: rcu: rcu_barrier VS cpu_hotplug: Ensure callbacks in dead cpu are migrated to o > > > > > > > > > > > > > > ? > > > > > > > > > > > > > > Ingo > > > > > > > > > > > > > > > > > > I tested three times the same things but with 04cb9ac and... it didn't triggered > > > > > > anymore :-) > > > > > > > > > > So lets hope that was the culprit. > > > > > > > > > > Great work Frederic! > > > > > > > > No new lockups of this nature in overnight -tip testing. It's > > > > still a bit too early to tell for sure but it's promising ;-) > > > > > > just got a lockup again :-/ It hangs here: > > > > > > calling init_mmio_trace+0x0/0x12 @ 1 > > > initcall init_mmio_trace+0x0/0x12 returned 0 after 0 usecs > > > calling init_graph_trace+0x0/0x12 @ 1 > > > Testing tracer function_graph: > > > > > > and this time i got good stackdumps as well - see below. Config > > > attached. > > > > > CONFIG_CLASSIC_RCU=y > > > > All the crashes you reported only happen with classic RCU. > > > > Paul, > > > > Did anything change recently that could cause this lockup? > > Arjan van de Ven is seeing a problem where a single > synchronize_rcu() during bootup is taking a full second, which is > currently thought to be due to some drivers spinning in the kernel > (Arjan is working on a bootgraph that will hopefully pinpoint the > problem: http://lkml.org/lkml/2009/3/21/7). If the drivers were > also instrumented with ftrace, they might (or might not)slow down > even further, depending on exactly why they are spinning.
for one of the hung boxes in the past i waited 24 hours but it never unwedged itself. The box that hung today is still hanging and the RCU stall detector is still busy printing out those backtraces.
Ingo
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