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Subject: Re: [RFC V3] mm: Generalize and rename notify_page_fault() as
 kprobe_page_fault()
From:   Leonardo Bras <leonardo@linux.ibm.com>
To:     Anshuman Khandual <anshuman.khandual@arm.com>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc:     Mark Rutland <mark.rutland@arm.com>,
        Michal Hocko <mhocko@suse.com>, linux-ia64@vger.kernel.org,
        linux-sh@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Paul Mackerras <paulus@samba.org>,
        Matthew Wilcox <willy@infradead.org>,
        sparclinux@vger.kernel.org, linux-s390@vger.kernel.org,
        Yoshinori Sato <ysato@users.sourceforge.jp>, x86@kernel.org,
        Russell King <linux@armlinux.org.uk>,
        Will Deacon <will.deacon@arm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-arm-kernel@lists.infradead.org,
        Tony Luck <tony.luck@intel.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linuxppc-dev@lists.ozlabs.org,
        "David S. Miller" <davem@davemloft.net>
Date:   Mon, 10 Jun 2019 12:27:02 -0300
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On Mon, 2019-06-10 at 08:09 +0530, Anshuman Khandual wrote:
> > > +    /*
> > > +     * To be potentially processing a kprobe fault and to be allowed
> > > +     * to call kprobe_running(), we have to be non-preemptible.
> > > +     */
> > > +    if (kprobes_built_in() && !preemptible() && !user_mode(regs)) {
> > > +        if (kprobe_running() && kprobe_fault_handler(regs, trap))
> >=20
> > don't need an 'if A if B', can do 'if A && B'
>=20
> Which will make it a very lengthy condition check.

Well, is there any problem line-breaking the if condition?

if (A && B && C &&
    D && E )

Also, if it's used only to decide the return value, maybe would be fine
to do somethink like that:

return (A && B && C &&
        D && E );=20

Regards,

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