Re: [PATCH v4 5/5] blktrace: Make init_blk_tracer() asynchronous when trace_async_init set
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2026-01-30 03:31:21
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Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
On Thu, 29 Jan 2026 22:26:08 -0500 Steven Rostedt [off-list ref] wrote:
Use trace_printk() instead. printk now has a "deferred" output. I'm not sure if the timestamps of when it prints is when the print took place or when it got to the console :-/
I added the below patch and have this result:
kworker/u33:1-79 [002] ..... 1.840855: trace_event_update_all: Start syncing
swapper/0-1 [005] ..... 6.045742: trace_eval_sync: sync maps
kworker/u33:1-79 [002] ..... 12.289296: trace_event_update_all: Finish syncing
swapper/0-1 [005] ..... 12.289387: trace_eval_sync: sync maps complete
Which shows that the final initcall waited for the work queue to complete:
-- Steve
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 396d59202438..33180d5622a8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c@@ -10817,9 +10817,11 @@ subsys_initcall(trace_eval_init); static int __init trace_eval_sync(void) { + trace_printk("sync maps\n"); /* Make sure the eval map updates are finished */ if (eval_map_wq) destroy_workqueue(eval_map_wq); + trace_printk("sync maps complete\n"); return 0; }
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index af6d1fe5cab7..194b344400e9 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c@@ -3555,6 +3555,7 @@ void trace_event_update_all(struct trace_eval_map **map, int len) int last_i; int i; + trace_printk("Start syncing\n"); down_write(&trace_event_sem); list_for_each_entry_safe(call, p, &ftrace_events, list) { /* events are usually grouped together with systems */
@@ -3593,6 +3594,8 @@ void trace_event_update_all(struct trace_eval_map **map, int len) cond_resched(); } up_write(&trace_event_sem); + msleep(10000); + trace_printk("Finish syncing\n"); } static bool event_in_systems(struct trace_event_call *call,