linux-kernel - Re: [GIT PULL] ftrace: Fixes for v6.13

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Message-ID: <20241215200950.5cb5c3d9@batman.local.home>
Date: Sun, 15 Dec 2024 20:09:50 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: "Theodore Ts'o" <tytso@....edu>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, LKML
 <linux-kernel@...r.kernel.org>, Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Al Viro <viro@...iv.linux.org.uk>, Michal
 Simek <monstr@...str.eu>
Subject: Re: [GIT PULL] ftrace: Fixes for v6.13

[
  I'm back from a lovely day with my wife and friends visiting the
  Finger Lake wineries which I would love to share with the Linux
  Plumbers attendees if we ever get to have Plumbers at the Ithaca
  Conference center. ;-)
]

On Sun, 15 Dec 2024 16:40:34 -0500
"Theodore Ts'o" <tytso@....edu> wrote:

> I'm not convinced that it's worth it in this particular case, so I
> think I side with Linus here; maybe all of this hackery isn't worth
> it?  Steven, what am I missing?  Why did we go down this particular
> path in the first place?  I assume there must have been something that
> seemed like a good reason at the time?

It has nothing to do with performance. It has only to do with debugging
and catching the issue where developers use "%s" in the TP_printk() of
TRACE_EVENT() for a string that can be freed after the trace event was
executed but before it is read from the ring buffer.

I stated in another email that I didn't like this solution when I wrote
it, but it was the only solution I could think of to catch this common
bug. But I also stated in another email that I think there's another
solution that doesn't deal with va_list implementations and should be
acceptable by Linus.

I'm not against ripping out the code. I agree with Linus that it's a
hack, but the hack that caught the bugs early seemed to me worth it at
the time.

-- Steve