From: "Paul E. McKenney" <paulmck@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
rcu@vger.kernel.org, Andrew Lutomirski <luto@kernel.org>,
X86 ML <x86@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Joel Fernandes <joel@joelfernandes.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH x86/entry: Force rcu_irq_enter() when in idle task
Date: Fri, 12 Jun 2020 14:56:50 -0700 [thread overview]
Message-ID: <20200612215650.GN4455@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <87k10ccc2n.fsf@nanos.tec.linutronix.de>
On Fri, Jun 12, 2020 at 09:34:56PM +0200, Thomas Gleixner wrote:
> Thomas Gleixner <tglx@linutronix.de> writes:
>
> > "Paul E. McKenney" <paulmck@kernel.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.
>
> After talking to Paul some more we came to the conclusion that the
> failure scenario of task rcu is not completely clear and the trigger
> scenario is obscure enough. This needs more investigation and the
> important part which we were chasing is fixed and agreed on. So I go
> with the simple version now and Paul will follow up once it can be
> properly explained.
So the whole TASKS03 failure issue turned out to be me applying the
wrong patches onto the wrong commits. Retesting with -tip x86/entry
passes TASKS03, as in more than 100 instances of it.
I am rerunning the whole stack, but I don't see the need to wait for
that. (I will be running increasingly long tests over Friday night,
Pacific Time.)
Thanx, Paul
next prev parent reply other threads:[~2020-06-12 21:56 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-11 23:53 [PATCH RFC] x86/entry: Ask RCU if it needs rcu_irq_{enter,exit}() Paul E. McKenney
2020-06-11 23:54 ` Paul E. McKenney
2020-06-12 5:30 ` Andy Lutomirski
2020-06-12 12:40 ` Thomas Gleixner
2020-06-12 13:55 ` [PATCH x86/entry: Force rcu_irq_enter() when in idle task Thomas Gleixner
2020-06-12 14:26 ` Frederic Weisbecker
2020-06-12 14:47 ` Thomas Gleixner
2020-06-12 15:32 ` Andy Lutomirski
2020-06-12 17:49 ` Paul E. McKenney
2020-06-12 19:19 ` Paul E. McKenney
2020-06-12 19:25 ` Thomas Gleixner
2020-06-12 19:28 ` Andy Lutomirski
2020-06-12 19:34 ` Thomas Gleixner
2020-06-12 21:56 ` Paul E. McKenney [this message]
2020-06-12 19:50 ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-06-15 20:16 ` [PATCH " Joel Fernandes
2020-06-16 8:40 ` Thomas Gleixner
2020-06-16 14:30 ` Joel Fernandes
2020-06-16 16:52 ` Andy Lutomirski
2020-06-12 9:27 ` [PATCH RFC] x86/entry: Ask RCU if it needs rcu_irq_{enter,exit}() Thomas Gleixner
2020-06-12 13:57 ` Paul E. McKenney
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