On Thu, 20 Apr 2017 15:11:54 +0200
Petr Mladek <pmladek@xxxxxxxx> wrote:
>
> >From c530d9dee91c74db5e6a198479e2e63b24cb84a2 Mon Sep 17 00:00:00 2001
> From: Petr Mladek <pmladek@xxxxxxxx>
> Date: Thu, 20 Apr 2017 10:52:31 +0200
> Subject: [PATCH] printk: Use the main logbuf in NMI when logbuf_lock is
> available
I tried this patch. It's better because I get the end of the trace, but
I do lose the beginning of it:
** 196358 printk messages dropped ** [ 102.321182] perf-5981 0.... 12983650us : d_path <-seq_path
The way I tested it was by adding this:
Index: linux-trace.git/kernel/trace/trace_functions.c
===================================================================
--- linux-trace.git.orig/kernel/trace/trace_functions.c
+++ linux-trace.git/kernel/trace/trace_functions.c
@@ -469,8 +469,11 @@ ftrace_cpudump_probe(unsigned long ip, u
struct trace_array *tr, struct ftrace_probe_ops *ops,
void *data)
{
- if (update_count(ops, ip, data))
- ftrace_dump(DUMP_ORIG);
+ char *killer = NULL;
+
+ panic_on_oops = 1; /* force panic */
+ wmb();
+ *killer = 1;
}
static int
Then doing the following:
# echo 1 > /proc/sys/kernel/ftrace_dump_on_oops
# trace-cmd start -p function
# echo nmi_handle:cpudump > /debug/tracing/set_ftrace_filter
# perf record -c 100 -a sleep 1
And that triggers the crash.
-- Steve
