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| author | Clément Léger <cleger@rivosinc.com> | 2023-09-29 21:16:37 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-10-25 11:16:55 +0200 |
| commit | 79700b56f17ddc28ca9f2b4c63d8dca288754897 (patch) | |
| tree | 90cf14ea3cc5dc996b478264935dc8bda09fe0b2 | |
| parent | ea7df52089490a703be5b7188f1a067c9b2b8ed7 (diff) | |
| download | linux-79700b56f17ddc28ca9f2b4c63d8dca288754897.tar.gz linux-79700b56f17ddc28ca9f2b4c63d8dca288754897.tar.bz2 linux-79700b56f17ddc28ca9f2b4c63d8dca288754897.zip | |
tracing: relax trace_event_eval_update() execution with cond_resched()
[ 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.
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/trace/trace_events.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index a3dc6c126b3e..ed39d3ec202e 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2242,6 +2242,7 @@ void trace_event_eval_update(struct trace_eval_map **map, int len) update_event_printk(call, map[i]); } } + cond_resched(); } up_write(&trace_event_sem); } |