patches/drivers-block-zram-Replace-bit-spinlocks-with-rtmute.patch

From: Mike Galbraith <umgwanakikbuti@gmail.com>
Date: Thu, 31 Mar 2016 04:08:28 +0200
Subject: [PATCH] drivers/block/zram: Replace bit spinlocks with rtmutex
 for -rt

They're nondeterministic, and lead to ___might_sleep() splats in -rt.
OTOH, they're a lot less wasteful than an rtmutex per page.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/block/zram/zram_drv.c |   26 ++++++++++++++++++++++++++
 drivers/block/zram/zram_drv.h |    3 +++
 2 files changed, 29 insertions(+)

--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -748,6 +748,30 @@ static DEVICE_ATTR_RO(io_stat);
 static DEVICE_ATTR_RO(mm_stat);
 static DEVICE_ATTR_RO(debug_stat);
 
+#ifdef CONFIG_PREEMPT_RT_BASE
+static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages)
+{
+	size_t index;
+
+	for (index = 0; index < num_pages; index++)
+		spin_lock_init(&zram->table[index].lock);
+}
+
+static void zram_slot_lock(struct zram *zram, u32 index)
+{
+	spin_lock(&zram->table[index].lock);
+	__set_bit(ZRAM_ACCESS, &zram->table[index].value);
+}
+
+static void zram_slot_unlock(struct zram *zram, u32 index)
+{
+	__clear_bit(ZRAM_ACCESS, &zram->table[index].value);
+	spin_unlock(&zram->table[index].lock);
+}
+
+#else
+static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) { }
+
 static void zram_slot_lock(struct zram *zram, u32 index)
 {
 	bit_spin_lock(ZRAM_ACCESS, &zram->table[index].value);
@@ -757,6 +781,7 @@ static void zram_slot_unlock(struct zram
 {
 	bit_spin_unlock(ZRAM_ACCESS, &zram->table[index].value);
 }
+#endif
 
 static void zram_meta_free(struct zram *zram, u64 disksize)
 {
@@ -786,6 +811,7 @@ static bool zram_meta_alloc(struct zram
 		return false;
 	}
 
+	zram_meta_init_table_locks(zram, num_pages);
 	return true;
 }
 
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -77,6 +77,9 @@ struct zram_table_entry {
 		unsigned long element;
 	};
 	unsigned long value;
+#ifdef CONFIG_PREEMPT_RT_BASE
+	spinlock_t lock;
+#endif
 };
 
 struct zram_stats {