[tip: locking/core] locking/local_lock: Add PREEMPT_RT support

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     026659b9774e4c586baeb457557fcfc4e0ad144b
Gitweb:        https://git.kernel.org/tip/026659b9774e4c586baeb457557fcfc4e0ad144b
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Sun, 15 Aug 2021 23:29:28 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 17 Aug 2021 19:08:49 +02:00

locking/local_lock: Add PREEMPT_RT support

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.

Co-developed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210815211306.023630962@xxxxxxxxxxxxx
---
 include/linux/local_lock_internal.h | 44 ++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+)

diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h
index 3f02b81..975e33b 100644
--- 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 +97,45 @@ 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 spinlock_t local_lock_t;
+
+#define INIT_LOCAL_LOCK(lockname) __LOCAL_SPIN_LOCK_UNLOCKED((lockname))
+
+#define __local_lock_init(l)					\
+	do {							\
+		local_spin_lock_init((l));			\
+	} while (0)
+
+#define __local_lock(__lock)					\
+	do {							\
+		migrate_disable();				\
+		spin_lock(this_cpu_ptr((__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)));		\
+		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 */