Messages in this thread | | | Date | Wed, 13 Mar 2024 15:14:28 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v2 0/4] perf: Make SIGTRAP and __perf_pending_irq() work on RT. |
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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...
- Arnaldo
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