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From: Mike Galbraith <umgwanakikbuti@gmail.com>
Date: Thu, 31 Mar 2016 04:08:28 +0200
Subject: [PATCH] zram: Replace bit spinlocks with spinlock_t for PREEMPT_RT.
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.7/older/patches-6.7-rt6.tar.xz
The bit spinlock disables preemption. The spinlock_t lock becomes a sleeping
lock on PREEMPT_RT and it can not be acquired in this context. In this locked
section, zs_free() acquires a zs_pool::lock, and there is access to
zram::wb_limit_lock.
Use a spinlock_t on PREEMPT_RT for locking and set/ clear ZRAM_LOCK bit after
the lock has been acquired/ dropped.
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lkml.kernel.org/r/YqIbMuHCPiQk+Ac2@linutronix.de
Link: https://lore.kernel.org/20230323161830.jFbWCosd@linutronix.de
---
drivers/block/zram/zram_drv.c | 37 +++++++++++++++++++++++++++++++++++++
drivers/block/zram/zram_drv.h | 3 +++
2 files changed, 40 insertions(+)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -57,6 +57,41 @@ static void zram_free_page(struct zram *
static int zram_read_page(struct zram *zram, struct page *page, u32 index,
struct bio *parent);
+#ifdef CONFIG_PREEMPT_RT
+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 int zram_slot_trylock(struct zram *zram, u32 index)
+{
+ int ret;
+
+ ret = spin_trylock(&zram->table[index].lock);
+ if (ret)
+ __set_bit(ZRAM_LOCK, &zram->table[index].flags);
+ return ret;
+}
+
+static void zram_slot_lock(struct zram *zram, u32 index)
+{
+ spin_lock(&zram->table[index].lock);
+ __set_bit(ZRAM_LOCK, &zram->table[index].flags);
+}
+
+static void zram_slot_unlock(struct zram *zram, u32 index)
+{
+ __clear_bit(ZRAM_LOCK, &zram->table[index].flags);
+ spin_unlock(&zram->table[index].lock);
+}
+
+#else
+
+static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) { }
+
static int zram_slot_trylock(struct zram *zram, u32 index)
{
return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags);
@@ -71,6 +106,7 @@ static void zram_slot_unlock(struct zram
{
bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags);
}
+#endif
static inline bool init_done(struct zram *zram)
{
@@ -1242,6 +1278,7 @@ static bool zram_meta_alloc(struct zram
if (!huge_class_size)
huge_class_size = zs_huge_class_size(zram->mem_pool);
+ zram_meta_init_table_locks(zram, num_pages);
return true;
}
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -69,6 +69,9 @@ struct zram_table_entry {
unsigned long element;
};
unsigned long flags;
+#ifdef CONFIG_PREEMPT_RT
+ spinlock_t lock;
+#endif
#ifdef CONFIG_ZRAM_MEMORY_TRACKING
ktime_t ac_time;
#endif
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