linux-kernel - [PATCH 0/2 v2] tracing: Fix ftrace_boot

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Date:   Tue, 04 Apr 2023 22:21:13 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ross Zwisler <zwisler@...gle.com>
Subject: [PATCH 0/2 v2] tracing: Fix ftrace_boot_snapshot command line

While debugging some boot up code, I found that the snapshots were
constantly triggering at boot up, even though there was no boot
snapshot specified. Looking into it, I found there were too bugs.

1) It would trigger a snapshot on any instance if one was created
   from the kernel command line.

2) The error handling would only affect the top level instance.
   So the fact that a snapshot was done on a instance that didn't
   allocate a buffer triggered a warning written into the top level
   buffer, and worse yet, disabled the top level buffer.

Changes since v1: https://lore.kernel.org/linux-trace-kernel/20230404230011.757302390@goodmis.org/

 - My tests failed due to tr->allocated_snapshot only being a field
   when CONFIG_TRACE_MAX_TRACE is defined. And it doesn't make sense
   doing any of that logic if it is not, as snapshots depend on that config.

This addresses both of the above bugs.

Steven Rostedt (Google) (2):
      tracing: Have tracing_snapshot_instance_cond() write errors to the appropriate instance
      tracing: Fix ftrace_boot_snapshot command line logic

----
 kernel/trace/trace.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)