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Message-ID: <87r1ukxf1b.fsf@nanos.tec.linutronix.de>
Date: Fri, 12 Jun 2020 21:25:20 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: paulmck@...nel.org
Cc: LKML <linux-kernel@...r.kernel.org>, rcu@...r.kernel.org,
Andrew Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
Frederic Weisbecker <frederic@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Joel Fernandes <joel@...lfernandes.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Will Deacon <will@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH x86/entry: Force rcu_irq_enter() when in idle task
"Paul E. McKenney" <paulmck@...nel.org> writes:
> On Fri, Jun 12, 2020 at 10:49:53AM -0700, Paul E. McKenney wrote:
>> I will therefore address this issue in a follow-on patch.
>
> I should add that -your- patch from yesterday did -not- cause this
> problem, in case that is of interest.
So I still can add it back and amend the changelog and comment:
Change the condition from !rcu_is_watching() to is_idle_task(current) ||
rcu_is_watching() which enforces that interrupts in the idle task
unconditionally invoke rcu_irq_enter() independent of the RCU state. For
most scenarios is_idle_task() would be sufficient but Task RCU needs it
according to Paul.
Thanks,
tglx
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