From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
The kernel command line ftrace_boot_snapshot by itself is supposed to
trigger a snapshot at the end of boot up of the main top level trace
buffer. A ftrace_boot_snapshot=foo will do the same for an instance called
foo that was created by trace_instance=foo,...
The logic was broken where if ftrace_boot_snapshot was by itself, it would
trigger a snapshot for all instances that had tracing enabled, regardless
if it asked for a snapshot or not.
When a snapshot is requested for a buffer, the buffer's
tr->allocated_snapshot is set to true. Use that to know if a trace buffer
wants a snapshot at boot up or not.
Since the top level buffer is part of the ftrace_trace_arrays list,
there's no reason to treat it differently than the other buffers. Just
iterate the list if ftrace_boot_snapshot was specified.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 9c1c251d670bc ("tracing: Allow boot instances to have snapshot buffers")
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
Changes since v1: https://lkml.kernel.org/r/20230404230308.501833715@xxxxxxxxxxx
- Protect use of tr->allocated_snapshot around #ifdef TRACER_MAX_TRACE
kernel/trace/trace.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 93740a9370c6..36a6037823cd 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -10394,19 +10394,20 @@ __init static int tracer_alloc_buffers(void)
void __init ftrace_boot_snapshot(void)
{
+#ifdef CONFIG_TRACER_MAX_TRACE
struct trace_array *tr;
- if (snapshot_at_boot) {
- tracing_snapshot();
- internal_trace_puts("** Boot snapshot taken **\n");
- }
+ if (!snapshot_at_boot)
+ return;
list_for_each_entry(tr, &ftrace_trace_arrays, list) {
- if (tr == &global_trace)
+ if (!tr->allocated_snapshot)
continue;
- trace_array_puts(tr, "** Boot snapshot taken **\n");
+
tracing_snapshot_instance(tr);
+ trace_array_puts(tr, "** Boot snapshot taken **\n");
}
+#endif
}
void __init early_trace_init(void)
--
2.39.2
