From: Mike Galbraith Date: Thu, 31 Mar 2016 04:08:28 +0200 Subject: [PATCH 1/3] zram: Replace bit spinlocks with a spinlock_t. Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.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. Add a spinlock_t for locking. Keep the set/ clear ZRAM_LOCK bit after the lock has been acquired/ dropped. The size of struct zram_table_entry increases by 4 bytes due to lock and additional 4 bytes padding with CONFIG_ZRAM_TRACK_ENTRY_ACTIME enabled. Signed-off-by: Mike Galbraith Reviewed-by: Sergey Senozhatsky Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/20240906141520.730009-2-bigeasy@linutronix.de --- drivers/block/zram/zram_drv.c | 18 ++++++++++++++---- drivers/block/zram/zram_drv.h | 1 + 2 files changed, 15 insertions(+), 4 deletions(-) --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -59,17 +59,24 @@ static int zram_read_page(struct zram *z static int zram_slot_trylock(struct zram *zram, u32 index) { - return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags); + 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) { - bit_spin_lock(ZRAM_LOCK, &zram->table[index].flags); + spin_lock(&zram->table[index].lock); + __set_bit(ZRAM_LOCK, &zram->table[index].flags); } static void zram_slot_unlock(struct zram *zram, u32 index) { - bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags); + __clear_bit(ZRAM_LOCK, &zram->table[index].flags); + spin_unlock(&zram->table[index].lock); } static inline bool init_done(struct zram *zram) @@ -1211,7 +1218,7 @@ static void zram_meta_free(struct zram * static bool zram_meta_alloc(struct zram *zram, u64 disksize) { - size_t num_pages; + size_t num_pages, index; num_pages = disksize >> PAGE_SHIFT; zram->table = vzalloc(array_size(num_pages, sizeof(*zram->table))); @@ -1226,6 +1233,9 @@ static bool zram_meta_alloc(struct zram if (!huge_class_size) huge_class_size = zs_huge_class_size(zram->mem_pool); + + for (index = 0; index < num_pages; index++) + spin_lock_init(&zram->table[index].lock); return true; } --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -69,6 +69,7 @@ struct zram_table_entry { unsigned long element; }; unsigned long flags; + spinlock_t lock; #ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME ktime_t ac_time; #endif