Re: [PATCH] rethook: Use tsk->on_cpu to check task execution state
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2026-05-26 03:37:21
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On Mon, 25 May 2026 21:22:53 +0800 Tengda Wu [off-list ref] wrote:
When a task calls schedule() to yield the CPU, its state remains TASK_RUNNING, but its stack is frozen and safe to walk. Replace task_is_running(tsk) with tsk->on_cpu to avoid overly conservative rejections.
Please see the Sashiko's comment. https://sashiko.dev/#/patchset/20260525132253.1889726-1-wutengda%40huaweicloud.com When calling Unwind on a task other than the current, IMHO, it is the responsibility of the caller of this function to ensure that the stack trace of that task is safe. We also should not use tsk->on_cpu, but should use task_on_cpu(tsk). BTW, should task_on_cpu() use READ_ONCE() etc? wait_task_inactive() seems a bit fragile. Thanks,
quoted hunk ↗ jump to hunk
Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook") Signed-off-by: Tengda Wu <redacted> --- kernel/trace/rethook.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 5a8bdf88999a..bd5e5f455e85 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c@@ -250,7 +250,7 @@ unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame if (WARN_ON_ONCE(!cur)) return 0; - if (tsk != current && task_is_running(tsk)) + if (tsk != current && tsk->on_cpu) return 0; do {-- 2.34.1
-- Masami Hiramatsu (Google) [off-list ref]