linux-kernel - Re: [PATCH tip/core/rcu 03/17] rcu/tree: Skip entry into the page allocator for PREEMPT

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Message-ID: <20200715142009.GA25196@pc636>
Date:   Wed, 15 Jul 2020 16:20:09 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Uladzislau Rezki <urezki@...il.com>, paulmck@...nel.org,
        joel@...lfernandes.org, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com
Subject: Re: [PATCH tip/core/rcu 03/17] rcu/tree: Skip entry into the page
 allocator for PREEMPT_RT

On Wed, Jul 15, 2020 at 04:16:22PM +0200, Sebastian Andrzej Siewior wrote:
> On 2020-07-15 15:38:08 [+0200], Uladzislau Rezki wrote:
> > > As of -rc3 it should complain about printk() which is why it is still disabled by default.
> > >
> > Have you tried to trigger a "complain" you are talking about?
> 
> No, but I is wrong because a raw_spinlock_t is acquired followed by a
> spinlock_t.
>
Right. According to documentation CONFIG_PROVE_RAW_LOCK_NESTING is used
to detect raw_spinlock vs. spinlock nesting usage.

> 
> > I suspect to get some trace dump when CONFIG_PROVE_RAW_LOCK_NESTING=y.
> 
> You should get one if you haven't received any splat earlier (like from
> printk code because it only triggers once).
> 
Got it.

Thanks! 

--
Vlad Rezki