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? > > > > Updated patch against -rcu below in case it is useful. > > I added more debug and got this: > > [ 215.097318] 4) | /* On unexpected CPU 4, expected 5!!! */ > [ 215.098285] 4) | /* Online CPUs: 0-7 Active CPUs: 0-7 */ > [ 215.099283] 4) | /* ret = 0, ->cpus_allowed 0-4,6-7 */ > > http://www.rdrop.com/~paulmck/submission/console.tpkm.log.gz > > The task's ->cpus_allowed got set to the bitwise not of the requested > mask. I took a quick scan through the code but don't see how this > happens. > > Very strange. > > Any suggestions for further debugging? Left to myself, I would copy > the requested cpumask to a per-task location and insert checks in the > sched_setaffinity() code path, crude and ugly though that might seem. > (Ugly enough that I will wait until tomorrow to try it out.)
And of course the nicer approach is to simply drop a few trace_printk() calls into sched_setaffinity(), which got me this (with other CPU tracing removed): [ 207.440153] 0) | /* sched_setaffinity: new_mask 5 */ [ 207.445567] 0) | /* On unexpected CPU 0, expected 5!!! */ [ 207.450017] 0) | /* Online CPUs: 0-7 Active CPUs: 0-7 */ [ 207.454943] 0) | /* ret = 0, ->cpus_allowed 0-4,6-7 */ http://www.rdrop.com/~paulmck/submission/console.tkpms.log.gz (Search for "->cpus_allowed".) I forward-ported the relevant patches from -rcu and placed them on -rcu branch peterz.2019.05.09a, and this is what produced the output above. Any other debugging thoughts? Or, if you wish, you can reproduce by running the following: 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" --kconfig "CONFIG_FUNCTION_TRACER=y CONFIG_FUNCTION_GRAPH_TRACER=y" This gets me the following summary output: --- Thu May 9 12:08:31 PDT 2019 Test summary: Results directory: /home/git/linux-2.6-tip/tools/testing/selftests/rcutorture/res/2019.05.09-12:08:31 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 --kconfig CONFIG_FUNCTION_TRACER=y CONFIG_FUNCTION_GRAPH_TRACER=y TRIVIAL ------- 2177 GPs (18.1417/s) [trivial: g0 f0x0 ] :CONFIG_HOTPLUG_CPU: improperly set WARNING: BAD SEQ 2176:2176 last:2177 version 4 /home/git/linux-2.6-tip/tools/testing/selftests/rcutorture/res/2019.05.09-12:08:31/TRIVIAL/console.log WARNING: Assertion failure in /home/git/linux-2.6-tip/tools/testing/selftests/rcutorture/res/2019.05.09-12:08:31/TRIVIAL/console.log WARNING: Summary: Warnings: 1 Bugs: 1 Call Traces: 5 Stalls: 8 Thanx, Paul
