linux-kernel - Re: [PATCH] ftrace: avoid replacing the list func with itself

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Message-ID: <20221121213402.154adf09@rorschach.local.home>
Date:   Mon, 21 Nov 2022 21:34:02 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Song Shuai <suagrfillet@...il.com>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: avoid replacing the list func with itself

On Tue, 22 Nov 2022 02:28:25 +0000
Song Shuai <suagrfillet@...il.com> wrote:

> Song Shuai <suagrfillet@...il.com> 于2022年10月26日周三 13:20写道：
> >
> > The list func (ftrace_ops_list_func) will be patched first
> > before the transition between old and new calls are set,
> > which fixed the race described in this commit `59338f75`.
> >
> > While ftrace_trace_function changes from the list func to a
> > ftrace_ops func, like unregistering the klp_ops to leave the only
> > global_ops in ftrace_ops_list, the ftrace_[regs]_call will be
> > replaced with the list func although it already exists. So there
> > should be a condition to avoid this.
> >
> > This patch backups saved_ftrace_func by saved_ftrace_func_old
> > which will be compared with the list func before trying to patch it.
> >  
> Ping...

Thanks for the ping. I had thought I had replied to this, but I don't
see it in my sent folder. I may have been distracted, and lost the
message.

I'll take a look at it tomorrow.

-- Steve