From: "Clément Léger" <cleger@rivosinc.com>
To: Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Clément Léger" <cleger@rivosinc.com>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
"Atish Patra" <atishp@rivosinc.com>
Subject: [PATCH v2] tracing: relax trace_event_eval_update() execution with cond_resched()
Date: Fri, 29 Sep 2023 21:16:37 +0200 [thread overview]
Message-ID: <20230929191637.416931-1-cleger@rivosinc.com> (raw)
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.
Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
Changes in v2:
- Use cond_resched() instead of schedule()
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);
}
--
2.40.1
next reply other threads:[~2023-09-29 19:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-29 19:16 Clément Léger [this message]
2023-09-29 20:14 ` [PATCH v2] tracing: relax trace_event_eval_update() execution with cond_resched() Atish Kumar Patra
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