linux-kernel - [patch V5 72/72] locking/local_lock: Add PREEMPT

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Message-ID: <20210815211306.023630962@linutronix.de>
Date:   Sun, 15 Aug 2021 23:29:28 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Davidlohr Bueso <dave@...olabs.net>,
        Mike Galbraith <efault@....de>
Subject: [patch V5 72/72] locking/local_lock: Add PREEMPT_RT support

From: Thomas Gleixner <tglx@...utronix.de>

On PREEMPT_RT enabled kernels local_lock maps to a per CPU 'sleeping'
spinlock which protects the critical section while staying preemptible. CPU
locality is established by disabling migration.

Provide the necessary types and macros to substitute the non-RT variant.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
V5: New patch
---
 include/linux/local_lock_internal.h |   48 ++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
--- a/include/linux/local_lock_internal.h
+++ b/include/linux/local_lock_internal.h
@@ -6,6 +6,8 @@
 #include <linux/percpu-defs.h>
 #include <linux/lockdep.h>
 
+#ifndef CONFIG_PREEMPT_RT
+
 typedef struct {
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	struct lockdep_map	dep_map;
@@ -95,3 +97,49 @@ do {								\
 		local_lock_release(this_cpu_ptr(lock));		\
 		local_irq_restore(flags);			\
 	} while (0)
+
+#else /* !CONFIG_PREEMPT_RT */
+
+/*
+ * On PREEMPT_RT local_lock maps to a per CPU spinlock which protects the
+ * critical section while staying preemptible.
+ */
+typedef struct {
+	spinlock_t		lock;
+} local_lock_t;
+
+#define INIT_LOCAL_LOCK(lockname) {				\
+		__LOCAL_SPIN_LOCK_UNLOCKED((lockname).lock)	\
+	}
+
+#define __local_lock_init(l)					\
+	do {							\
+		local_spin_lock_init(&(l)->lock);		\
+	} while (0)
+
+#define __local_lock(__lock)					\
+	do {							\
+		migrate_disable();				\
+		spin_lock(&(this_cpu_ptr((__lock)))->lock);	\
+	} while (0)
+
+#define __local_lock_irq(lock)			__local_lock(lock)
+
+#define __local_lock_irqsave(lock, flags)			\
+	do {							\
+		typecheck(unsigned long, flags);		\
+		flags = 0;					\
+		__local_lock(lock);				\
+	} while (0)
+
+#define __local_unlock(__lock)					\
+	do {							\
+		spin_unlock(&(this_cpu_ptr((__lock)))->lock);	\
+		migrate_enable();				\
+	} while (0)
+
+#define __local_unlock_irq(lock)		__local_unlock(lock)
+
+#define __local_unlock_irqrestore(lock, flags)	__local_unlock(lock)
+
+#endif /* CONFIG_PREEMPT_RT */