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>,
	sparclinux@vger.kernel.org, linux-s390@vger.kernel.org,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	x86@kernel.org, Russell King <linux@armlinux.org.uk>,
	Matthew Wilcox <willy@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Will Deacon <will.deacon@arm.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>
Subject: Re: [RFC V3] mm: Generalize and rename notify_page_fault() as kprobe_page_fault()
Date: Tue, 11 Jun 2019 17:31:12 +0000	[thread overview]
Message-ID: <bec5983d50e37953b3962a6e53fca0a243c7158b.camel@linux.ibm.com> (raw)
In-Reply-To: <7b0a7afd-2776-0d95-19c5-3e15959744eb@arm.com>

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On Tue, 2019-06-11 at 10:44 +0530, Anshuman Khandual wrote:
> 
> 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.
> 
Sure, I agree with them. It's way more readable.

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