| Message ID | 20230323161830.jFbWCosd@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | zram: Replace bit spinlocks with spinlock_t for PREEMPT_RT. | expand |
On (23/03/23 17:18), Sebastian Andrzej Siewior wrote: > From: Mike Galbraith <umgwanakikbuti@gmail.com> > > 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 > --- > > I'm simply forwarding Mike's patch here. The other alternative is to let > the driver depend on !PREEMPT_RT. I can't tell likely it is that this > driver is used. Mike most likely stumbled upon it while running LTP. Yeah, I'm curious if anyone uses zram in preempt-rt systems. I don't mind this patch but would be nice to add new code when it solves some real problems. Maybe `depend on !PREEMPT_RT` can be a better option.
On Fri, 2023-03-24 at 13:07 +0900, Sergey Senozhatsky wrote: > On (23/03/23 17:18), Sebastian Andrzej Siewior wrote: > > Mike most likely stumbled upon it while running LTP. > > Yeah, I'm curious if anyone uses zram in preempt-rt systems. I don't > mind this patch but would be nice to add new code when it solves some > real problems. Maybe `depend on !PREEMPT_RT` can be a better option. Patchlet's job here is only obese config RT vs !RT testing. It can always move back into local_patches, it won't be lonely ;-) -Mike
--- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -57,6 +57,40 @@ 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) { @@ -72,6 +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) { @@ -1311,6 +1346,7 @@ 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