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authorClément Léger <cleger@rivosinc.com>2023-09-29 21:16:37 +0200
committerSteven Rostedt (Google) <rostedt@goodmis.org>2023-09-30 16:24:55 -0400
commit23cce5f25491968b23fb9c399bbfb25f13870cd9 (patch)
tree38c3459a5628bd3eed67f9bfd2f061e5503ba7fc
parent1e0cb399c7653462d9dadf8ab9425337c355d358 (diff)
tracing: relax trace_event_eval_update() execution with cond_resched()
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>
-rw-r--r--kernel/trace/trace_events.c1
1 files changed, 1 insertions, 0 deletions
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);
}