[PATCH bpf-next] rethook: Remove warning messages printed for finding return address of a frame.

[Kui-Feng Lee <thinker.li@gmail.com>]

rethook_find_ret_addr() prints a warning message and returns 0 when the
target task is running and not the "current" task to prevent returning an
incorrect return address. However, this check is incomplete as the target
task can still transition to the running state when finding the return
address, although it is safe with RCU.

The issue we encounter is that the kernel frequently prints warning
messages when BPF profiling programs call to bpf_get_task_stack() on
running tasks.

The callers should be aware and willing to take the risk of receiving an
incorrect return address from a task that is currently running other than
the "current" one. A warning is not needed here as the callers are intent
on it.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
---
 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 fa03094e9e69..4297a132a7ae 100644
--- a/kernel/trace/rethook.c
+++ b/kernel/trace/rethook.c
@@ -248,7 +248,7 @@ unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame
 	if (WARN_ON_ONCE(!cur))
 		return 0;
 
-	if (WARN_ON_ONCE(tsk != current && task_is_running(tsk)))
+	if (tsk != current && task_is_running(tsk))
 		return 0;
 
 	do {
-- 
2.34.1