On Wed, 05 Apr 2023 09:58:15 -0400 Steven Rostedt rostedt@goodmis.org wrote:
From: "Steven Rostedt (Google)" rostedt@goodmis.org
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.
Link: https://lkml.kernel.org/r/20230405022341.895334039@goodmis.org
Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Ross Zwisler zwisler@google.com Fixes: 9c1c251d670bc ("tracing: Allow boot instances to have snapshot buffers")
I guess I didn't need to Cc stable here, as the commit it fixed was added in the 6.3 merge window.
$ git describe --contains 9c1c251d670bc v6.3-rc1~126^2~8
Oh well.
-- Steve
Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org
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 ed1d1093f5e9..4686473b8497 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -10393,19 +10393,20 @@ __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)