Subject: drivers/block/zram: Replace bit spinlocks with rtmutex for -rt From: Mike Galbraith Date: Thu Mar 31 04:08:28 2016 +0200 From: Mike Galbraith 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 Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner --- drivers/block/zram/zram_drv.c | 36 ++++++++++++++++++++++++++++++++++++ drivers/block/zram/zram_drv.h | 1 + 2 files changed, 37 insertions(+) --- --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -59,6 +59,40 @@ static void zram_free_page(struct zram * static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, u32 index, int offset, struct bio *bio); +#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) { @@ -74,6 +108,7 @@ 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) { @@ -1169,6 +1204,7 @@ 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 @@ -63,6 +63,7 @@ struct zram_table_entry { unsigned long element; }; unsigned long flags; + spinlock_t lock; #ifdef CONFIG_ZRAM_MEMORY_TRACKING ktime_t ac_time; #endif