Messages in this thread |  | | | Date | Fri, 20 Mar 2009 21:48:48 +0100 | | From | Frederic Weisbecker <> | | Subject | Re: [PATCH 0/5] [GIT PULL] updates for tip/tracing/ftrace |
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On Fri, Mar 20, 2009 at 08:54:14PM +0100, Ingo Molnar wrote: > > * Frederic Weisbecker <fweisbec@gmail.com> wrote: > > > On Fri, Mar 20, 2009 at 08:27:21PM +0100, Ingo Molnar wrote: > > > > > > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > > > > > > > On Fri, Mar 20, 2009 at 07:38:49PM +0100, Ingo Molnar wrote: > > > > > > > > > > * Ingo Molnar <mingo@elte.hu> wrote: > > > > > > > > > > > > > This looks like it is RCU/stop_machine related. The CPU is > > > > > > > > stuck in in stop_machine? I see that rcu_torture is running. > > > > > > > > Does this go away if you turn off rcu_torture? > > > > > > > > > > > > > > Grasping at straws... Does Lai's rcu_barrier() fix help? > > > > > > > > > > > > which one is that? > > > > > > > > > > ok, found it. Will know in about ~24 hours whether it helps. > > > > > > > > http://lkml.org/lkml/2009/3/20/71 was the one I was thinking of, > > > > just to double-check. > > > > > > Yeah - i just picked it up into tip:core/rcu. > > > > > > I didnt immediately connect the two things, as 'tracer self-test' > > > does not lend itself to 'CPU hotplug and RCU race fix' - but indeed > > > in the case of the function tracer there's a dependency due to > > > stop_machine_run(). Thanks for point it out! > > > > > > Ingo > > > > > > I've successfully triggered a crash, the problem is that I can't be sure this is > > the same because I don't have a serial line on my x86-64, and the trace goes too far. > > Moreover boot_delay=N make it disappear. > > > > I can trigger it each time I boot with ftrace=function_graph and > > the following patch applied: > > > > diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c > > index 7c4142a..e9914a8 100644 > > --- a/kernel/rcutorture.c > > +++ b/kernel/rcutorture.c > > @@ -616,7 +616,7 @@ rcu_torture_writer(void *arg) > > static DEFINE_RCU_RANDOM(rand); > > > > VERBOSE_PRINTK_STRING("rcu_torture_writer task started"); > > - set_user_nice(current, 19); > > + set_user_nice(current, -1); > > > > do { > > schedule_timeout_uninterruptible(1); > > @@ -736,7 +736,7 @@ rcu_torture_reader(void *arg) > > struct timer_list t; > > > > 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 :-)
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