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 <CAAYs2=iOvP-TxLs+_QFMLQHG86xi2PYK_CN_rXUWHBx=kY+1aw@mail.gmail.com> <20221121213402.154adf09@rorschach.local.home>
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From:   Song Shuai <suagrfillet@gmail.com>
Date:   Tue, 22 Nov 2022 02:37:37 +0000
Message-ID: <CAAYs2=jVXkA53P35D62=TqQx9tr_cQbqXUex6Pg0y710m=yExw@mail.gmail.com>
Subject: Re: [PATCH] ftrace: avoid replacing the list func with itself
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     mingo@redhat.com, linux-kernel@vger.kernel.org
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Steven Rostedt <rostedt@goodmis.org> =E4=BA=8E2022=E5=B9=B411=E6=9C=8822=E6=
=97=A5=E5=91=A8=E4=BA=8C 02:34=E5=86=99=E9=81=93=EF=BC=9A
>
> On Tue, 22 Nov 2022 02:28:25 +0000
> Song Shuai <suagrfillet@gmail.com> wrote:
>
> > Song Shuai <suagrfillet@gmail.com> =E4=BA=8E2022=E5=B9=B410=E6=9C=8826=
=E6=97=A5=E5=91=A8=E4=B8=89 13:20=E5=86=99=E9=81=93=EF=BC=9A
> > >
> > > 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