Messages in this thread | | | Date | Wed, 13 Mar 2024 15:30:52 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v2 0/4] perf: Make SIGTRAP and __perf_pending_irq() work on RT. |
| |
On Wed, Mar 13, 2024 at 03:14:28PM -0300, Arnaldo Carvalho de Melo wrote: > On Wed, Mar 13, 2024 at 12:23:32PM -0300, Arnaldo Carvalho de Melo wrote: > > On Wed, Mar 13, 2024 at 03:35:27PM +0100, Marco Elver wrote: > > > On Tue, 12 Mar 2024 at 19:08, Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote: > > > > Arnaldo reported that "perf test sigtrap" fails on PREEMPT_RT. Sending > > > > the signal gets delayed until event_sched_out() which then uses > > > > task_work_add() for its delivery. This breaks on PREEMPT_RT because the > > > > signal is delivered with disabled preemption. > > > > > While looking at this, I also stumbled upon __perf_pending_irq() which > > > > requires disabled interrupts but this is not the case on PREEMPT_RT. > > > > > This series aim to address both issues while not introducing a new issue > > > > at the same time ;) > > > > Any testing is appreciated. > > > > > v1…v2: https://lore.kernel.org/all/20240308175810.2894694-1-bigeasy@linutronix.de/ > > > > - Marco pointed me to the testsuite that showed two problems: > > > > - Delayed task_work from NMI / missing events. > > > > Fixed by triggering dummy irq_work to enforce an interrupt for > > > > the exit-to-userland path which checks task_work > > > > - Increased ref-count on clean up/ during exec. > > > > Mostly addressed by the former change. There is still a window > > > > if the NMI occurs during execve(). This is addressed by removing > > > > the task_work before free_event(). > > > > The testsuite (remove_on_exec) fails sometimes if the event/ > > > > SIGTRAP is sent before the sighandler is installed. > > > > > Tested-by: Marco Elver <elver@google.com>
> > > It does pass the tests in tools/testing/selftests/perf_events (non-RT > > > kernel, lockdep enabled). But I do recall this being a particularly > > > sharp corner of perf, so any additional testing and review here is > > > useful. > > > Right, I'm testing with the full 'perf test' suite now. > > 'perf test' doesn't show any regression, now I'm running Vince Weaver's > https://github.com/deater/perf_event_tests, storing the results with > this patchset and then without, to do a diff, lets see...
[root@nine perf_event_tests]# diff -u results.6.8.0-rc7-rt6 results.6.8.0-rc7.sebastian-rt6+ | grep ^[+-] --- results.6.8.0-rc7-rt6 2024-03-13 15:26:37.923323518 -0300 +++ results.6.8.0-rc7.sebastian-rt6+ 2024-03-13 15:14:11.505333801 -0300 -Linux nine 6.8.0-rc7-rt6 #1 SMP PREEMPT_RT Fri Mar 8 17:36:48 -03 2024 x86_64 x86_64 x86_64 GNU/Linux +Linux nine 6.8.0-rc7.sebastian-rt6+ #2 SMP PREEMPT_RT Tue Mar 12 18:01:31 -03 2024 x86_64 x86_64 x86_64 GNU/Linux - Testing "branch-misses" generalized event... FAILED + Testing "branch-misses" generalized event... PASSED - Testing uncore events... SKIPPED + Testing uncore events... PASSED - We are running release 6.8.0-rc7-rt6 + We are running release 6.8.0-rc7.sebastian-rt6+ - Running on CPU 4 + Running on CPU 2 - Running on CPU 6 + Running on CPU 2 - Measuring on CPU 5 -Running on CPU 6 -Measuring on CPU 5 + Measuring on CPU 6 +Running on CPU 2 +Measuring on CPU 6 [root@nine perf_event_tests]#
So basically:
- Testing "branch-misses" generalized event... FAILED + Testing "branch-misses" generalized event... PASSED - Testing uncore events... SKIPPED + Testing uncore events... PASSED
So things improved! I'll re-run to see if these results are stable...
- Arnaldo
| |