From: fabio de francesco <fabio@metanix.org>
To: "chxanders@gmail.com" <chxanders@gmail.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: linux/kernel/sched.c: context_switch().
Date: Wed, 8 Sep 2010 15:54:07 +0200 [thread overview]
Message-ID: <201009081554.08676.fabio@metanix.org> (raw)
In-Reply-To: <AANLkTi=mNJhoODzZqLpTC8QqqnwLgWxVXEJzXviF64mV@mail.gmail.com>
On Wednesday 08 September 2010 15:22:07 you wrote:
> but there is a ! not operator, !mm means mm != 0 , or the other way it
> is saying it is unlikey(mm is NULL)
Ok. Let me point to Linux-2.6.32. You may see that there the opposite is
written. Can you please explain why they changed unlikely with likely passing
from 2.6.32 to 2.6.33?
> On 8 September 2010 20:18, fabio de francesco <fabio@metanix.org> wrote:
> > On Wednesday 08 September 2010 15:10:49 you wrote:
> >> Long day? Do you mean likely(!mm) actually means unlikely(0)?
> >
> > No, no. I am sorry for my poor English. I mean:"likely(!mm) is like
> > "likely(0)".
> >
> >> On 8 September 2010 20:08, fabio de francesco <fabio@metanix.org> wrote:
> >> > There must be something I am missing in sched.c at context_switch()
> >> > function definition.
> >> >
> >> > There I can read the following code:
> >> >
> >> > static inline void
> >> > context_switch(struct rq *rq, struct task_struct *prev,
> >> > struct task_struct *next)
> >> > {
> >> > ...
> >> > struct mm_struct *mm;
> >> > mm = next->mm;
> >> > if (likely(!mm)) {
> >> > next->active_mm = oldmm;
> >> > atomic_inc(&oldmm->mm_count);
> >> > enter_lazy_tlb(oldmm, next);
> >> > } else
> >> > switch_mm(oldmm, mm, next);
> >> > ...
> >> > }
> >> >
> >> > May someone please explain why the mm pointer is likely supposed to be
> >> > NULL?
> >> >
> >> > Thanks in advance.
> >> >
> >> > fabio
> >> > --
> >> > To unsubscribe from this list: send the line "unsubscribe
> >> > linux-kernel" in the body of a message to majordomo@vger.kernel.org
> >> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >> > Please read the FAQ at http://www.tux.org/lkml/
next prev parent reply other threads:[~2010-09-08 13:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-08 13:08 linux/kernel/sched.c: context_switch() fabio de francesco
2010-09-08 13:10 ` chxanders
2010-09-08 13:23 ` fabio de francesco
[not found] ` <201009081518.21569.fabio@metanix.org>
[not found] ` <AANLkTi=mNJhoODzZqLpTC8QqqnwLgWxVXEJzXviF64mV@mail.gmail.com>
2010-09-08 13:54 ` fabio de francesco [this message]
-- strict thread matches above, loose matches on Subject: below --
2010-09-08 12:33 fabio de francesco
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