From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Scott Wood <swood@redhat.com>
Cc: paulmck@kernel.org,
Valentin Schneider <valentin.schneider@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org,
linux-rt-users@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Steven Price <steven.price@arm.com>,
Ard Biesheuvel <ardb@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>, Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH] rcutorture: Avoid problematic critical section nesting on RT
Date: Fri, 20 Aug 2021 09:11:06 +0200 [thread overview]
Message-ID: <20210820071106.fba7l6ikgo7aa6xm@linutronix.de> (raw)
In-Reply-To: <561ab28b18c31fbc221f4cb0c4df6db9b0538675.camel@redhat.com>
On 2021-08-19 23:11:12 [-0500], Scott Wood wrote:
> On Thu, 2021-08-19 at 11:20 -0700, Paul E. McKenney wrote:
> > On Thu, Aug 19, 2021 at 05:47:08PM +0200, Sebastian Andrzej Siewior wrote:
> > > On 2021-08-19 17:39:29 [+0200], To Paul E. McKenney wrote:
> > > > + /*
> > > > + * Ideally these sequences would be detected in debug builds
> > > > + * (regardless of RT), but until then don't stop testing
> > > > + * them on non-RT.
> > > > + */
> > > > + if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
> > > > + /*
> > > > + * Can't release the outermost rcu lock in an irq disabled
> > > > + * section without preemption also being disabled, if irqs
> > > > + * had ever been enabled during this RCU critical section
> > > > + * (could leak a special flag and delay reporting the qs).
> > > > + */
> > > > + if ((oldmask & RCUTORTURE_RDR_RCU) &&
> > > > + (mask & RCUTORTURE_RDR_IRQ) &&
> > > > + !(mask & preempts))
> > > > + mask |= RCUTORTURE_RDR_RCU;
> > >
> > > 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.
>
> Yeah, I think this was to deal with not having the irq work stuff in RT
> at the time.
Good. Thank you for the confirmation.
I run (without the hunk above) 2x 6h of TREE01 and 4x 6h of TREE06 and
it looked good.
> -Scott
Sebastian
next prev parent reply other threads:[~2021-08-20 7:11 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 20:13 [PATCH v3 0/4] rcu, arm64: PREEMPT_RT fixlets Valentin Schneider
2021-08-11 20:13 ` [PATCH v3 1/4] rcutorture: Don't disable softirqs with preemption disabled when PREEMPT_RT Valentin Schneider
2021-08-12 16:47 ` Paul E. McKenney
2021-08-17 12:13 ` Sebastian Andrzej Siewior
2021-08-17 13:17 ` Sebastian Andrzej Siewior
2021-08-17 14:40 ` [PATCH] rcutorture: Avoid problematic critical section nesting on RT Sebastian Andrzej Siewior
2021-08-18 22:46 ` Paul E. McKenney
2021-08-19 15:35 ` Sebastian Andrzej Siewior
2021-08-19 15:39 ` Sebastian Andrzej Siewior
2021-08-19 15:47 ` Sebastian Andrzej Siewior
2021-08-19 18:20 ` Paul E. McKenney
2021-08-19 18:45 ` Sebastian Andrzej Siewior
2021-08-20 4:11 ` Scott Wood
2021-08-20 7:11 ` Sebastian Andrzej Siewior [this message]
2021-08-20 7:42 ` [PATCH v2] rcutorture: Avoid problematic critical section nesting on PREEMPT_RT Sebastian Andrzej Siewior
2021-08-20 22:10 ` Paul E. McKenney
2021-08-20 3:23 ` [PATCH] rcutorture: Avoid problematic critical section nesting on RT Scott Wood
2021-08-20 6:54 ` Sebastian Andrzej Siewior
2021-08-11 20:13 ` [PATCH v3 2/4] sched: Introduce migratable() Valentin Schneider
2021-08-17 14:43 ` Sebastian Andrzej Siewior
2021-08-22 17:31 ` Valentin Schneider
2021-08-17 17:09 ` Sebastian Andrzej Siewior
2021-08-17 19:30 ` Phil Auld
2021-08-22 18:14 ` Valentin Schneider
2022-01-26 16:56 ` Sebastian Andrzej Siewior
2022-01-26 18:10 ` Valentin Schneider
2022-01-27 10:07 ` Sebastian Andrzej Siewior
2022-01-27 18:23 ` Valentin Schneider
2022-01-27 19:27 ` Valentin Schneider
2022-02-04 9:24 ` Sebastian Andrzej Siewior
2021-08-11 20:13 ` [PATCH v3 3/4] rcu/nocb: Protect NOCB state via local_lock() under PREEMPT_RT Valentin Schneider
2021-08-13 0:20 ` Paul E. McKenney
2021-08-13 18:48 ` Valentin Schneider
2021-08-24 13:00 ` Frederic Weisbecker
2021-08-17 15:36 ` Sebastian Andrzej Siewior
2021-08-22 18:15 ` Valentin Schneider
2021-09-21 14:05 ` Thomas Gleixner
2021-09-21 21:12 ` rcu/tree: Protect rcu_rdp_is_offloaded() invocations on RT Thomas Gleixner
2021-09-21 23:36 ` Frederic Weisbecker
2021-09-22 2:18 ` Paul E. McKenney
2021-09-22 11:31 ` Frederic Weisbecker
2021-09-21 23:45 ` Frederic Weisbecker
2021-09-22 6:32 ` Sebastian Andrzej Siewior
2021-09-22 11:10 ` Frederic Weisbecker
2021-09-22 11:27 ` Sebastian Andrzej Siewior
2021-09-22 11:38 ` Frederic Weisbecker
2021-09-22 13:02 ` Sebastian Andrzej Siewior
2021-09-23 10:02 ` Frederic Weisbecker
2021-09-30 9:00 ` Valentin Schneider
2021-09-30 10:53 ` Frederic Weisbecker
2021-09-30 13:22 ` Valentin Schneider
2021-08-11 20:13 ` [PATCH v3 4/4] arm64: mm: Make arch_faults_on_old_pte() check for migratability Valentin Schneider
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