linux-kernel - Re: [PATCH v2 4/6] powerpc: use common ptrace_syscall_enter hook to handle _TIF_SYSCALL

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Date:   Mon, 18 Mar 2019 17:40:28 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Richard Weinberger <richard@....at>, jdike@...toit.com,
        Steve Capper <Steve.Capper@....com>,
        Haibo Xu <haibo.xu@....com>, Bin Lu <bin.lu@....com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2 4/6] powerpc: use common ptrace_syscall_enter hook to
 handle _TIF_SYSCALL_EMU

On Mon, Mar 18, 2019 at 06:33:41PM +0100, Oleg Nesterov wrote:
> On 03/18, Sudeep Holla wrote:
> >
> > On Mon, Mar 18, 2019 at 06:20:24PM +0100, Oleg Nesterov wrote:
> > >
> > > Again, to me this patch just makes the code look worse. Honestly, I don't
> > > think that the new (badly named) ptrace_syscall_enter() hook makes any sense.
> > >
> >
> > Worse because we end up reading current_thread_info->flags twice ?
>
> Mostly because in my opinion ptrace_syscall_enter() buys nothing but makes
> the caller's code less readable/understandable.
>
> Sure, this is subjective.
>

Based on what we have in that function today, I tend to agree. Will and
Richard were in the opinion to consolidate SYSEMU handling(in the threads
pointed in my cover letter). If there's a better way to achieve the same
I am in for it. I have just tried to put something together based on
what I could think of.

--
Regards,
Sudeep