From: Scott Wood <swood@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Valentin Schneider <valentin.schneider@arm.com>
Cc: 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>,
"Paul E. McKenney" <paulmck@kernel.org>,
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: Thu, 19 Aug 2021 22:23:37 -0500 [thread overview]
Message-ID: <20b9051fe47b7068ed3496bd7f5d417b1af69e3a.camel@redhat.com> (raw)
In-Reply-To: <20210817144018.nqssoq475vitrqlv@linutronix.de>
On Tue, 2021-08-17 at 16:40 +0200, Sebastian Andrzej Siewior wrote:
> [bigeasy: remove 'preempt_disable(); local_bh_disable(); preempt_enable();
> local_bh_enable();' from the examples because this works on RT now. ]
Does it actually work? If preemption is disabled during local_bh_disable,
softirq_ctrl.lock won't be taken. If you then get preempted between the
preempt_enable() and the local_bh_enable(), and another task tries to do
local_bh_disable(), won't it successfully get softirq_ctrl.lock, add to
softirq_ctrl.cnt, and proceed right into the critical section?
Or am I missing something?
-Scott
WARNING: multiple messages have this Message-ID (diff)
From: Scott Wood <swood@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Valentin Schneider <valentin.schneider@arm.com>
Cc: 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>,
"Paul E. McKenney" <paulmck@kernel.org>,
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: Thu, 19 Aug 2021 22:23:37 -0500 [thread overview]
Message-ID: <20b9051fe47b7068ed3496bd7f5d417b1af69e3a.camel@redhat.com> (raw)
In-Reply-To: <20210817144018.nqssoq475vitrqlv@linutronix.de>
On Tue, 2021-08-17 at 16:40 +0200, Sebastian Andrzej Siewior wrote:
> [bigeasy: remove 'preempt_disable(); local_bh_disable(); preempt_enable();
> local_bh_enable();' from the examples because this works on RT now. ]
Does it actually work? If preemption is disabled during local_bh_disable,
softirq_ctrl.lock won't be taken. If you then get preempted between the
preempt_enable() and the local_bh_enable(), and another task tries to do
local_bh_disable(), won't it successfully get softirq_ctrl.lock, add to
softirq_ctrl.cnt, and proceed right into the critical section?
Or am I missing something?
-Scott
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next prev parent reply other threads:[~2021-08-20 3:23 UTC|newest]
Thread overview: 102+ 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 ` Valentin Schneider
2021-08-11 20:13 ` [PATCH v3 1/4] rcutorture: Don't disable softirqs with preemption disabled when PREEMPT_RT Valentin Schneider
2021-08-11 20:13 ` Valentin Schneider
2021-08-12 16:47 ` Paul E. McKenney
2021-08-12 16:47 ` Paul E. McKenney
2021-08-17 12:13 ` Sebastian Andrzej Siewior
2021-08-17 12:13 ` Sebastian Andrzej Siewior
2021-08-17 13:17 ` 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
2021-08-17 14:40 ` Sebastian Andrzej Siewior
2021-08-18 22:46 ` Paul E. McKenney
2021-08-18 22:46 ` Paul E. McKenney
2021-08-19 15:35 ` Sebastian Andrzej Siewior
2021-08-19 15:35 ` Sebastian Andrzej Siewior
2021-08-19 15:39 ` Sebastian Andrzej Siewior
2021-08-19 15:39 ` Sebastian Andrzej Siewior
2021-08-19 15:47 ` Sebastian Andrzej Siewior
2021-08-19 15:47 ` Sebastian Andrzej Siewior
2021-08-19 18:20 ` Paul E. McKenney
2021-08-19 18:20 ` Paul E. McKenney
2021-08-19 18:45 ` Sebastian Andrzej Siewior
2021-08-19 18:45 ` Sebastian Andrzej Siewior
2021-08-20 4:11 ` Scott Wood
2021-08-20 4:11 ` Scott Wood
2021-08-20 7:11 ` Sebastian Andrzej Siewior
2021-08-20 7:11 ` Sebastian Andrzej Siewior
2021-08-20 7:42 ` [PATCH v2] rcutorture: Avoid problematic critical section nesting on PREEMPT_RT Sebastian Andrzej Siewior
2021-08-20 7:42 ` Sebastian Andrzej Siewior
2021-08-20 22:10 ` Paul E. McKenney
2021-08-20 22:10 ` Paul E. McKenney
2021-08-20 3:23 ` Scott Wood [this message]
2021-08-20 3:23 ` [PATCH] rcutorture: Avoid problematic critical section nesting on RT Scott Wood
2021-08-20 6:54 ` Sebastian Andrzej Siewior
2021-08-20 6:54 ` Sebastian Andrzej Siewior
2021-08-11 20:13 ` [PATCH v3 2/4] sched: Introduce migratable() Valentin Schneider
2021-08-11 20:13 ` Valentin Schneider
2021-08-17 14:43 ` Sebastian Andrzej Siewior
2021-08-17 14:43 ` Sebastian Andrzej Siewior
2021-08-22 17:31 ` Valentin Schneider
2021-08-22 17:31 ` Valentin Schneider
2021-08-17 17:09 ` Sebastian Andrzej Siewior
2021-08-17 17:09 ` Sebastian Andrzej Siewior
2021-08-17 19:30 ` Phil Auld
2021-08-17 19:30 ` Phil Auld
2021-08-22 18:14 ` Valentin Schneider
2021-08-22 18:14 ` Valentin Schneider
2022-01-26 16:56 ` Sebastian Andrzej Siewior
2022-01-26 16:56 ` Sebastian Andrzej Siewior
2022-01-26 18:10 ` Valentin Schneider
2022-01-26 18:10 ` Valentin Schneider
2022-01-27 10:07 ` Sebastian Andrzej Siewior
2022-01-27 10:07 ` Sebastian Andrzej Siewior
2022-01-27 18:23 ` Valentin Schneider
2022-01-27 18:23 ` Valentin Schneider
2022-01-27 19:27 ` Valentin Schneider
2022-01-27 19:27 ` Valentin Schneider
2022-02-04 9:24 ` Sebastian Andrzej Siewior
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
2021-08-11 20:13 ` Valentin Schneider
2021-08-13 0:20 ` Paul E. McKenney
2021-08-13 0:20 ` Paul E. McKenney
2021-08-13 18:48 ` Valentin Schneider
2021-08-13 18:48 ` Valentin Schneider
2021-08-24 13:00 ` Frederic Weisbecker
2021-08-17 15:36 ` Sebastian Andrzej Siewior
2021-08-17 15:36 ` Sebastian Andrzej Siewior
2021-08-22 18:15 ` Valentin Schneider
2021-08-22 18:15 ` Valentin Schneider
2021-09-21 14:05 ` Thomas Gleixner
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
2021-09-21 23:36 ` Frederic Weisbecker
2021-09-22 2:18 ` Paul E. McKenney
2021-09-22 2:18 ` Paul E. McKenney
2021-09-22 11:31 ` Frederic Weisbecker
2021-09-22 11:31 ` Frederic Weisbecker
2021-09-21 23:45 ` Frederic Weisbecker
2021-09-21 23:45 ` Frederic Weisbecker
2021-09-22 6:32 ` Sebastian Andrzej Siewior
2021-09-22 6:32 ` Sebastian Andrzej Siewior
2021-09-22 11:10 ` Frederic Weisbecker
2021-09-22 11:10 ` Frederic Weisbecker
2021-09-22 11:27 ` Sebastian Andrzej Siewior
2021-09-22 11:27 ` Sebastian Andrzej Siewior
2021-09-22 11:38 ` Frederic Weisbecker
2021-09-22 11:38 ` Frederic Weisbecker
2021-09-22 13:02 ` Sebastian Andrzej Siewior
2021-09-22 13:02 ` Sebastian Andrzej Siewior
2021-09-23 10:02 ` Frederic Weisbecker
2021-09-23 10:02 ` Frederic Weisbecker
2021-09-30 9:00 ` Valentin Schneider
2021-09-30 9:00 ` Valentin Schneider
2021-09-30 10:53 ` Frederic Weisbecker
2021-09-30 10:53 ` Frederic Weisbecker
2021-09-30 13:22 ` Valentin Schneider
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
2021-08-11 20:13 ` Valentin Schneider
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