From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 9 Apr 2014 11:58:17 +0200
Subject: percpu_ida: Use local locks
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.6/older/patches-4.6.2-rt5.tar.xz

the local_irq_save() + spin_lock() does not work that well on -RT

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 lib/percpu_ida.c |   20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

--- a/lib/percpu_ida.c
+++ b/lib/percpu_ida.c
@@ -26,6 +26,9 @@
 #include <linux/string.h>
 #include <linux/spinlock.h>
 #include <linux/percpu_ida.h>
+#include <linux/locallock.h>
+
+static DEFINE_LOCAL_IRQ_LOCK(irq_off_lock);
 
 struct percpu_ida_cpu {
 	/*
@@ -148,13 +151,13 @@ int percpu_ida_alloc(struct percpu_ida *
 	unsigned long flags;
 	int tag;
 
-	local_irq_save(flags);
+	local_lock_irqsave(irq_off_lock, flags);
 	tags = this_cpu_ptr(pool->tag_cpu);
 
 	/* Fastpath */
 	tag = alloc_local_tag(tags);
 	if (likely(tag >= 0)) {
-		local_irq_restore(flags);
+		local_unlock_irqrestore(irq_off_lock, flags);
 		return tag;
 	}
 
@@ -173,6 +176,7 @@ int percpu_ida_alloc(struct percpu_ida *
 
 		if (!tags->nr_free)
 			alloc_global_tags(pool, tags);
+
 		if (!tags->nr_free)
 			steal_tags(pool, tags);
 
@@ -184,7 +188,7 @@ int percpu_ida_alloc(struct percpu_ida *
 		}
 
 		spin_unlock(&pool->lock);
-		local_irq_restore(flags);
+		local_unlock_irqrestore(irq_off_lock, flags);
 
 		if (tag >= 0 || state == TASK_RUNNING)
 			break;
@@ -196,7 +200,7 @@ int percpu_ida_alloc(struct percpu_ida *
 
 		schedule();
 
-		local_irq_save(flags);
+		local_lock_irqsave(irq_off_lock, flags);
 		tags = this_cpu_ptr(pool->tag_cpu);
 	}
 	if (state != TASK_RUNNING)
@@ -221,7 +225,7 @@ void percpu_ida_free(struct percpu_ida *
 
 	BUG_ON(tag >= pool->nr_tags);
 
-	local_irq_save(flags);
+	local_lock_irqsave(irq_off_lock, flags);
 	tags = this_cpu_ptr(pool->tag_cpu);
 
 	spin_lock(&tags->lock);
@@ -253,7 +257,7 @@ void percpu_ida_free(struct percpu_ida *
 		spin_unlock(&pool->lock);
 	}
 
-	local_irq_restore(flags);
+	local_unlock_irqrestore(irq_off_lock, flags);
 }
 EXPORT_SYMBOL_GPL(percpu_ida_free);
 
@@ -345,7 +349,7 @@ int percpu_ida_for_each_free(struct perc
 	struct percpu_ida_cpu *remote;
 	unsigned cpu, i, err = 0;
 
-	local_irq_save(flags);
+	local_lock_irqsave(irq_off_lock, flags);
 	for_each_possible_cpu(cpu) {
 		remote = per_cpu_ptr(pool->tag_cpu, cpu);
 		spin_lock(&remote->lock);
@@ -367,7 +371,7 @@ int percpu_ida_for_each_free(struct perc
 	}
 	spin_unlock(&pool->lock);
 out:
-	local_irq_restore(flags);
+	local_unlock_irqrestore(irq_off_lock, flags);
 	return err;
 }
 EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);
