[Xenomai] Slow execution of RT task

Philippe Gerum rpm at xenomai.org
Tue Apr 15 16:40:10 CEST 2014

On 04/14/2014 02:45 PM, Jeroen Van den Keybus wrote:
>> .config would help. TIA,
> I've attached both the one for the 3.10 and the 3.8 kernels. In the
> meantime I found out that the 3.8 kernel exhibits the same problem.
> Please let know if attachments don't work. I'll paste into e-mail
> immediately (but personally I don't like .configs in the archive...).

I can't reproduce this bug using your configuration, so we need a 
different approach.

Could you patch the code fragment in, enable CONFIG_IPIPE_TRACE, then 
get a dump from /proc/ipipe/trace/frozen once the warning has triggered?
Maybe getting a bit more context by setting 
/proc/ipipe/trace/backtrace_points to 2048 would help too. TIA,

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 3538001..a1f09e3 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -477,6 +477,8 @@ void rcu_irq_exit(void)
  	rdtp = &__get_cpu_var(rcu_dynticks);
  	oldval = rdtp->dynticks_nesting;
+	if (rdtp->dynticks_nesting < 0)
+		ipipe_trace_freeze(0);
  	WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
  	if (rdtp->dynticks_nesting)
  		trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);


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