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@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211306.023630962@linutronix.de

diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h
index 3f02b81..975e33b 100644 (file)
--- 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 */