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Subject: Re: [RFC V3] mm: Generalize and rename notify_page_fault() as
 kprobe_page_fault()
To:     Leonardo Bras <leonardo@linux.ibm.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>
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From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <7b0a7afd-2776-0d95-19c5-3e15959744eb@arm.com>
Date:   Tue, 11 Jun 2019 10:44:00 +0530
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On 06/10/2019 08:57 PM, Leonardo Bras wrote:
> 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))
>>>
>>> don't need an 'if A if B', can do 'if A && B'
>>
>> 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 ); 

Got it. But as Dave and Matthew had pointed out earlier, the current x86
implementation has better readability. Hence will probably stick with it.