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Date:   Thu, 4 May 2023 15:21:11 -0300
From:   Wander Lairson Costa <wander@redhat.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
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        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Will Deacon <will@kernel.org>,
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        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v7 2/3] sched/task: Add the put_task_struct_atomic_safe()
 function
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On Thu, May 04, 2023 at 05:24:24PM +0200, Peter Zijlstra wrote:
> On Thu, May 04, 2023 at 11:55:15AM -0300, Wander Lairson Costa wrote:
> 
> > > Then I'm thinking something trivial like so:
> > >
> > > static inline void put_task_struct(struct task_struct *t)
> > > {
> > >         if (!refcount_dec_and_test(&t->usage))
> > >                 return;
> > >
> > >         if (IS_ENABLED(CONFIG_PREEMPT_RT) && !preemptible())
> > >                 call_rcu(&t->rcu, __put_task_struct_rcu);
> > >
> > >         __put_task_struct(t);
> > > }
> > >
> > 
> > That's what v5 [1] does. What would be the path in this case? Should I
> > resend it as v8?
> 
> It's almost what v5 does. v5 also has a !in_task() thing. v5 also
> violates codingstyle :-)

IIRC, the in_task() is there because preemptible() doesn't check if it
is running in interrupt context.

> 
> But yeah.. something like that.
>