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Date:   Sat,  7 Oct 2023 20:48:52 -0400
From:   Sasha Levin <>
Cc:     Clément Léger <>,
        Masami Hiramatsu <>,
        Atish Patra <>,
        Steven Rostedt <>,
        Sasha Levin <>,
Subject: [PATCH AUTOSEL 6.5 18/18] tracing: relax trace_event_eval_update() execution with cond_resched()

From: Clément Léger <>

[ Upstream commit 23cce5f25491968b23fb9c399bbfb25f13870cd9 ]

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.


Cc: Masami Hiramatsu <>
Signed-off-by: Clément Léger <>
Tested-by: Atish Patra <>
Reviewed-by: Atish Patra <>
Signed-off-by: Steven Rostedt (Google) <>
Signed-off-by: Sasha Levin <>
 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 0cf84a7449f5b..9841589b4af7f 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2777,6 +2777,7 @@ void trace_event_eval_update(struct trace_eval_map **map, int len)
 				update_event_fields(call, map[i]);
+		cond_resched();

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