From: "tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
x86 <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: [tip: sched/core] sched/rt: Provide migrate_disable/enable() inlines
Date: Sun, 09 Feb 2020 19:11:41 -0000 [thread overview]
Message-ID: <158127550143.411.9644440031937252653.tip-bot2@tip-bot2> (raw)
In-Reply-To: <878slclv1u.fsf@nanos.tec.linutronix.de>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 9fe65747dbacf0c9fcf12350c3afb5fcf7e78534
Gitweb: https://git.kernel.org/tip/9fe65747dbacf0c9fcf12350c3afb5fcf7e78534
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Sat, 08 Feb 2020 20:48:29 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sun, 09 Feb 2020 20:07:41 +01:00
sched/rt: Provide migrate_disable/enable() inlines
Code which solely needs to prevent migration of a task uses
preempt_disable()/enable() pairs. This is the only reliable way to do so
as setting the task affinity to a single CPU can be undone by a
setaffinity operation from a different task/process.
RT provides a seperate migrate_disable/enable() mechanism which does not
disable preemption to achieve the semantic requirements of a (almost) fully
preemptible kernel.
As it is unclear from looking at a given code path whether the intention is
to disable preemption or migration, introduce migrate_disable/enable()
inline functions which can be used to annotate code which merely needs to
disable migration. Map them to preempt_disable/enable() for now. The RT
substitution will be provided later.
Code which is annotated that way documents that it has no requirement to
protect against reentrancy of a preempting task. Either this is not
required at all or the call sites are already serialized by other means.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/878slclv1u.fsf@nanos.tec.linutronix.de
---
include/linux/preempt.h | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index bbb68db..bc3f1ae 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -322,4 +322,34 @@ static inline void preempt_notifier_init(struct preempt_notifier *notifier,
#endif
+/**
+ * migrate_disable - Prevent migration of the current task
+ *
+ * Maps to preempt_disable() which also disables preemption. Use
+ * migrate_disable() to annotate that the intent is to prevent migration,
+ * but not necessarily preemption.
+ *
+ * Can be invoked nested like preempt_disable() and needs the corresponding
+ * number of migrate_enable() invocations.
+ */
+static __always_inline void migrate_disable(void)
+{
+ preempt_disable();
+}
+
+/**
+ * migrate_enable - Allow migration of the current task
+ *
+ * Counterpart to migrate_disable().
+ *
+ * As migrate_disable() can be invoked nested, only the outermost invocation
+ * reenables migration.
+ *
+ * Currently mapped to preempt_enable().
+ */
+static __always_inline void migrate_enable(void)
+{
+ preempt_enable();
+}
+
#endif /* __LINUX_PREEMPT_H */
next prev parent reply other threads:[~2020-02-09 19:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-08 19:48 sched: Provide migrate_disable/enable() inlines Thomas Gleixner
2020-02-09 19:08 ` Ingo Molnar
2020-02-09 19:11 ` tip-bot2 for Thomas Gleixner [this message]
2020-02-20 20:20 ` [tip: sched/rt] sched/rt: " tip-bot2 for Thomas Gleixner
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