[PATCH] tracing: Report TP_printk double dereference with pr_warn()

[David Carlier <devnexen@gmail.com>]

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.

Fixes: b5cc230af5e5 ("tracing: Warn when an event dereferences a pointer in TP_printk()")
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 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);
 				return;
 			}
 			if (!isalnum(*ptr) && *ptr != '_')
-- 
2.55.0