linux-kernel - Re: [PATCH] rcutorture: Avoid problematic critical section nesting on RT

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Message-ID: <20210819184523.laa5vwvfsgotbgx5@linutronix.de>
Date:   Thu, 19 Aug 2021 20:45:23 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        rcu@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Steven Price <steven.price@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Mike Galbraith <efault@....de>, Scott Wood <swood@...hat.com>
Subject: Re: [PATCH] rcutorture: Avoid problematic critical section nesting
 on RT

On 2021-08-19 11:20:35 [-0700], Paul E. McKenney wrote:
> > This piece above, I don't understand. I had it running for a while and
> > it didn't explode. Let me try TREE01 for 30min without that piece.
> 
> This might be historical.  There was a time when interrupts being
> disabled across rcu_read_unlock() meant that preemption had to have
> been disabled across the entire RCU read-side critical section.
> 
> I am not seeing a purpose for it now, but I could easily be missing
> something, especially given my tenuous grasp of RT.

Okay. So the 30min test didn't trigger any warnings…

> Either way, looking forward to the next version!

Good. So if you liked what you have seen then I'm going to resubmit the
above as a proper patch then.
Thanks!

> 							Thanx, Paul

Sebastian