Messages in this thread | | | Date | Sat, 30 Sep 2023 16:41:05 -0400 | From | Steven Rostedt <> | Subject | Re: [for-linus][PATCH 2/4] tracing: relax trace_event_eval_update() execution with cond_resched() |
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[ The problem with sending email with quilt. It doesn't handle UTF-8 well :-/ ]
On Sat, 30 Sep 2023 16:32:15 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> From: =?UTF-8?q?Cl=C3=A9ment=20L=C3=A9ger?= <cleger@rivosinc.com> > > When kernel is compiled without preemption, the eval_map_work_func() > (which calls trace_event_eval_update()) will not be preempted up to its > complete execution. This can actually cause a problem since if another > CPU call stop_machine(), the call will have to wait for the > eval_map_work_func() function to finish executing in the workqueue > before being able to be scheduled. This problem was observe on a SMP > system at boot time, when the CPU calling the initcalls executed > clocksource_done_booting() which in the end calls stop_machine(). We > observed a 1 second delay because one CPU was executing > eval_map_work_func() and was not preempted by the stop_machine() task. > > Adding a call to cond_resched() in trace_event_eval_update() allows > other tasks to be executed and thus continue working asynchronously > like before without blocking any pending task at boot time. > > Link: https://lore.kernel.org/linux-trace-kernel/20230929191637.416931-1-cleger@rivosinc.com > > Cc: Masami Hiramatsu <mhiramat@kernel.org> > Signed-off-by: Clément Léger <cleger@rivosinc.com> > Tested-by: Atish Patra <atishp@rivosinc.com> > Reviewed-by: Atish Patra <atishp@rivosinc.com> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > kernel/trace/trace_events.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c > index 91951d038ba4..f49d6ddb6342 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -2770,6 +2770,7 @@ void trace_event_eval_update(struct trace_eval_map **map, int len) > update_event_fields(call, map[i]); > } > } > + cond_resched(); > } > up_write(&trace_event_sem); > }
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