Re: [PATCH] tracing: Report TP_printk double dereference with pr_warn()
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2026-08-06 21:41:12
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On Thu, 6 Aug 2026 06:07:16 +0100 David Carlier [off-list ref] 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.
quoted hunk ↗ jump to hunk
Signed-off-by: David Carlier <redacted> --- 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 != '_')