On Thu, May 09, 2019 at 10:36:54AM -0700, Paul E. McKenney wrote: > On Tue, May 07, 2019 at 03:16:13PM -0700, Paul E. McKenney wrote: > > 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?
And I can finally see/reproduce it!! Frankly, no idea how this is happening (I have been staring at these traces/functions for hours/days now... ;-/ ) Adding some "sched" folks in Cc: hopefully, they can shed some light about this. And yes, my only suggestion/approach would be to keep bisecting this code with printk*..., 'fun' ;-/ Andrea
