On Wed, 05 Apr 2023 09:58:15 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > 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. > > Link: https://lkml.kernel.org/r/20230405022341.895334039@xxxxxxxxxxx > > Cc: stable@xxxxxxxxxxxxxxx > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Ross Zwisler <zwisler@xxxxxxxxxx> > 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@xxxxxxxxxxx> > --- > 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)
