On Wed, May 01, 2019 at 01:27:13PM -0700, Paul E. McKenney wrote:
> On Wed, May 01, 2019 at 03:16:55PM -0400, Steven Rostedt wrote:
> > On Wed, 1 May 2019 12:12:13 -0700
> > "Paul E. McKenney" <paul...@linux.ibm.com> wrote:
> >
> >
> > > OK, what I did was to apply the patch at the end of this email to -rcu
> > > branch dev, then run rcutorture as follows:
> > >
> > > nohup tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 8 --duration 2
> > > --configs "TRIVIAL" --bootargs
> > > "trace_event=sched:sched_switch,sched:sched_wakeup ftrace=function_graph
> > > ftrace_graph_filter=sched_setaffinity,migration_cpu_stop"
> > >
> > > This resulted in the console output that I placed here:
> > >
> > > http://www2.rdrop.com/~paulmck/submission/console.log.gz
> > >
> > > But I don't see calls to sched_setaffinity() or migration_cpu_stop().
> > > Steve, is something else needed on the kernel command line in addition to
> > > the following?
> > >
> > > ftrace=function_graph
> > > ftrace_graph_filter=sched_setaffinity,migration_cpu_stop
> >
> > Do you have function graph enabled in the config?
> >
> > [ 2.098303] ftrace bootup tracer 'function_graph' not registered.
>
> I guess I don't! Thank you, will fix.
>
> Let's see...
>
> My .config has CONFIG_HAVE_FUNCTION_GRAPH_TRACER=y. It looks like I
> need CONFIG_FUNCTION_GRAPH_TRACER=y, which I don't have. And it looks
> like that needs CONFIG_FUNCTION_TRACER=y, which I also don't have.
> But I do have CONFIG_HAVE_FUNCTION_TRACER=y. So I should add this
> to my rcutorture command line:
>
> --kconfig "CONFIG_FUNCTION_TRACER=y CONFIG_FUNCTION_GRAPH_TRACER=y".
>
> I fired this up. Here is hoping! ;-)
>
> And it does have sched_setaffinity(), woo-hoo!!! I overwrote the old file:
>
> http://www2.rdrop.com/~paulmck/submission/console.log.gz
And I reran after adding a trace_printk(), which shows up as follows:
[ 211.409565] 6) | /* On unexpected CPU 6, expected 4!!! */
I placed the console log here:
http://www2.rdrop.com/~paulmck/submission/console.tpk.log.gz
Just in case the earlier log proves useful.
And it is acting as if the destination CPU proved to be offline. Except
that this rcutorture scenario doesn't offline anything, and I don't see
any CPU-hotplug removal messages. So I added another trace_printk() to
print out cpu_online_mask. This gets me the following:
[ 31.565605] 0) | /* On unexpected CPU 0, expected 1!!! */
[ 31.565605] 0) | /* Online CPUs: 0-7 */
So we didn't make it to CPU 1 despite its being online. I placed the
console log here:
http://www2.rdrop.com/~paulmck/submission/console.tpkol.log.gz
Thoughts?
Updated patch against -rcu below in case it is useful.
Thanx, Paul
------------------------------------------------------------------------
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index da04b5073dc3..23ec8ec7eddd 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -680,12 +680,24 @@ static struct rcu_torture_ops tasks_ops = {
static void synchronize_rcu_trivial(void)
{
int cpu;
+ int destcpu;
+ static int dont_trace;
for_each_online_cpu(cpu) {
- while (raw_smp_processor_id() != cpu)
- rcutorture_sched_setaffinity(current->pid,
- cpumask_of(cpu));
- WARN_ON_ONCE(raw_smp_processor_id() != cpu);
+ if (!READ_ONCE(dont_trace))
+ tracing_on();
+ rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
+ destcpu = raw_smp_processor_id();
+ if (destcpu == cpu) {
+ tracing_off();
+ } else {
+ trace_printk("On unexpected CPU %d, expected %d!!!\n",
destcpu, cpu);
+ trace_printk("Online CPUs: %*pbl\n",
cpumask_pr_args(cpu_online_mask));
+ tracing_stop();
+ WRITE_ONCE(dont_trace, 1);
+ WARN_ON_ONCE(1);
+ rcu_ftrace_dump(DUMP_ALL);
+ }
}
}
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index caffee644932..edaf0ca22ff7 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3495,6 +3495,7 @@ void __init rcu_init(void)
rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
WARN_ON(!rcu_par_gp_wq);
srcu_init();
+ tracing_off();
}
#include "tree_stall.h"
