linux-kernel - Re: [PATCH v4 07/15] lockdep: Implement crossrelease feature

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Date:   Fri, 13 Jan 2017 14:02:29 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Lai Jiangshan <jiangshanlai+lkml@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, walken@...gle.com,
        Boqun Feng <boqun.feng@...il.com>, kirill@...temov.name,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        npiggin@...il.com
Subject: Re: [PATCH v4 07/15] lockdep: Implement crossrelease feature

On Fri, Jan 13, 2017 at 12:39:04PM +0800, Lai Jiangshan wrote:
> > +
> > +/*
> > + * No contention. Irq disable is only required.
> > + */
> > +static int same_context_plock(struct pend_lock *plock)
> > +{
> > +       struct task_struct *curr = current;
> > +       int cpu = smp_processor_id();
> > +
> > +       /* In the case of hardirq context */
> > +       if (curr->hardirq_context) {
> > +               if (plock->hardirq_id != per_cpu(hardirq_id, cpu) ||
> > +                   plock->hardirq_context != curr->hardirq_context)
> > +                       return 0;
> > +       /* In the case of softriq context */
> > +       } else if (curr->softirq_context) {
> > +               if (plock->softirq_id != per_cpu(softirq_id, cpu) ||
> > +                   plock->softirq_context != curr->softirq_context)
> > +                       return 0;
> > +       /* In the case of process context */
> > +       } else {
> > +               if (plock->hardirq_context != 0 ||
> > +                   plock->softirq_context != 0)
> > +                       return 0;
> > +       }
> > +       return 1;
> > +}
> >
> 
> I have not read the code yet...
> but different work functions in workqueues are different "contexts" IMO,
> does commit operation work well in work functions?

Hello,

Yes. I also think it should be considered since each work might be run in
different context from another, thanks to concurrency support of workqueue.
I will reflect it.

Thanks,
Byungchul