linux-kernel - Re: [RFC 09/10] x86/mm: Rework lazy TLB to track the actual loaded mm

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Message-ID: <20170510055727.g6wojjiis36a6nvm@gmail.com>
Date:   Wed, 10 May 2017 07:57:27 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Nadav Amit <namit@...are.com>, Michal Hocko <mhocko@...e.com>,
        Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [RFC 09/10] x86/mm: Rework lazy TLB to track the actual loaded mm


* Thomas Gleixner <tglx@...utronix.de> wrote:

> On Sun, 7 May 2017, Andy Lutomirski wrote:
> >  /* context.lock is held for us, so we don't need any locking. */
> >  static void flush_ldt(void *current_mm)
> >  {
> > +	struct mm_struct *mm = current_mm;
> >  	mm_context_t *pc;
> >  
> > -	if (current->active_mm != current_mm)
> > +	if (this_cpu_read(cpu_tlbstate.loaded_mm) != current_mm)
> 
> While functional correct, this really should compare against 'mm'.
> 
> >  		return;
> >  
> > -	pc = &current->active_mm->context;
> > +	pc = &mm->context;

So this appears to be the function:

 static void flush_ldt(void *current_mm)
 {
        struct mm_struct *mm = current_mm;
        mm_context_t *pc;

        if (this_cpu_read(cpu_tlbstate.loaded_mm) != current_mm)
                return;

        pc = &mm->context;
        set_ldt(pc->ldt->entries, pc->ldt->size);
 }

why not rename 'current_mm' to 'mm' and remove the 'mm' local variable?

Thanks,

	Ingo