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

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Message-ID: <CAAYs2=jVXkA53P35D62=TqQx9tr_cQbqXUex6Pg0y710m=yExw@mail.gmail.com>
Date:   Tue, 22 Nov 2022 02:37:37 +0000
From:   Song Shuai <suagrfillet@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: avoid replacing the list func with itself

Steven Rostedt <rostedt@...dmis.org> 于2022年11月22日周二 02:34写道：
>
> 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
No problem, thanks!

-- Song