On Thu, 6 Aug 2026 06:07:16 +0100
David Carlier <[email protected]> wrote:
> test_double_dereference() uses WARN_ONCE(), which is per-call-site. Only
> the first offending event in the kernel is ever reported, and the tree
> still has six: ice_{rx,tx}_dim_template, two hfi1 txq events, mtu3_ep and
> edma_log_io. Whichever registers first hides the rest, and it taints the
> kernel for what is a source-level mistake.
>
> Use pr_warn() instead, matching the "TRACE EVENT ERROR:" report that
> handle_dereference_arg() already emits for the same class of problem.
> All offenders are now listed on one boot.
NAK!
>
> Fixes: b5cc230af5e5 ("tracing: Warn when an event dereferences a pointer in
> TP_printk()")
This is by no way a fix!
I want a big splat when this is triggered. It is a bug and needs to be
fixed immediately. pr_warn() does not make tests fail. I want this to fail
tests. I want this to panic when panic_on_warn is set.
> Signed-off-by: David Carlier <[email protected]>
> ---
> kernel/trace/trace_events.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index a8590d2394e3..53f32752edc0 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -415,8 +415,8 @@ static void test_double_dereference(const char *str, int
> len,
> ptr += 5;
> for (; ptr < end; ptr++) {
> if (ptr[0] == '-' && ptr[1] == '>') {
> - WARN_ONCE(1, "Event %s has double dereference
> in TP_printk: %.*s\n",
> - trace_event_name(call), len, str);
> + pr_warn("TRACE EVENT ERROR: Event %s has double
> dereference in TP_printk: %.*s\n",
> + trace_event_name(call), len, str);
Now I am OK with adding a pr_warn() with the WARN_ONCE() but the
WARN_ONCE() must stay. But leave off the fixes tag.
-- Steve
> return;
> }
> if (!isalnum(*ptr) && *ptr != '_')
