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Howlett" , Christoph Lameter , David Rientjes Cc: Roman Gushchin , Harry Yoo , Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org, vbabka@suse.cz, Sebastian Andrzej Siewior , Davidlohr Bueso , Alexei Starovoitov X-Mailer: b4 0.14.2 X-Stat-Signature: qgb6w7oa1kcrhhq85tcy53suyggk74w3 X-Rspamd-Queue-Id: 48B8E4000E X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1742222015-262225 X-HE-Meta: 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 sJNpdNvx XkaIHBLgVd/cXeHJ9LUud9UFTlHLjc+4R7cMnRVXnZsQHgKu1HwJiTGd7Ul4aSR2Cm4jfcjZIBO2vYUyV0v2FgD7HPxKsH8gLvE3Pw2mwHflRiEHY3cFnlV1N7Cmqq64i7Ybzy7GqLWyFnlpw7wER7woeAveAUBe6TWAjW40ApJrpb3kwxt/bbcpSgQ70LIreHnFBBZQgsiyZ7mn1m4n/rQo1npmb9LkF4nv1HKbOJJsQnZGmeAlUZ53FQiB2AhggImFqLFJLuOuj6TjcQsoQz9eGG/MG0TI1gEkr9WbRfQR0ccBq0b5Izxab+Su+2ADijJOoAEY4lmbJVxmdkPeeJuzHm73JU9zpU6ltybXFlrAxYQIYk+WTWnFbB3qezBke2dJIxzhAcQtQ2aFqOFGYIQdvFw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Sebastian Andrzej Siewior In !PREEMPT_RT local_lock_irqsave() disables interrupts to protect critical section, but it doesn't prevent NMI, so the fully reentrant code cannot use local_lock_irqsave() for exclusive access. Introduce localtry_lock_t and localtry_lock_irqsave() that disables interrupts and sets acquired=1, so localtry_lock_irqsave() from NMI attempting to acquire the same lock will return false. In PREEMPT_RT local_lock_irqsave() maps to preemptible spin_lock(). Map localtry_lock_irqsave() to preemptible spin_trylock(). When in hard IRQ or NMI return false right away, since spin_trylock() is not safe due to explicit locking in the underneath rt_spin_trylock() implementation. Removing this explicit locking and attempting only "trylock" is undesired due to PI implications. Note there is no need to use local_inc for acquired variable, since it's a percpu variable with strict nesting scopes. Acked-by: Davidlohr Bueso Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Vlastimil Babka Link: https://lore.kernel.org/r/20250222024427.30294-2-alexei.starovoitov@gmail.com Signed-off-by: Alexei Starovoitov --- include/linux/local_lock.h | 70 +++++++++++++++++ include/linux/local_lock_internal.h | 146 ++++++++++++++++++++++++++++++++++++ 2 files changed, 216 insertions(+) diff --git a/include/linux/local_lock.h b/include/linux/local_lock.h index 091dc0b6bdfb9f4721f94d19828a38fbfa59346c..1a0bc35839e360d5c8170105849c3883463852f8 100644 --- a/include/linux/local_lock.h +++ b/include/linux/local_lock.h @@ -51,6 +51,76 @@ #define local_unlock_irqrestore(lock, flags) \ __local_unlock_irqrestore(lock, flags) +/** + * localtry_lock_init - Runtime initialize a lock instance + */ +#define localtry_lock_init(lock) __localtry_lock_init(lock) + +/** + * localtry_lock - Acquire a per CPU local lock + * @lock: The lock variable + */ +#define localtry_lock(lock) __localtry_lock(lock) + +/** + * localtry_lock_irq - Acquire a per CPU local lock and disable interrupts + * @lock: The lock variable + */ +#define localtry_lock_irq(lock) __localtry_lock_irq(lock) + +/** + * localtry_lock_irqsave - Acquire a per CPU local lock, save and disable + * interrupts + * @lock: The lock variable + * @flags: Storage for interrupt flags + */ +#define localtry_lock_irqsave(lock, flags) \ + __localtry_lock_irqsave(lock, flags) + +/** + * localtry_trylock - Try to acquire a per CPU local lock. + * @lock: The lock variable + * + * The function can be used in any context such as NMI or HARDIRQ. Due to + * locking constrains it will _always_ fail to acquire the lock in NMI or + * HARDIRQ context on PREEMPT_RT. + */ +#define localtry_trylock(lock) __localtry_trylock(lock) + +/** + * localtry_trylock_irqsave - Try to acquire a per CPU local lock, save and disable + * interrupts if acquired + * @lock: The lock variable + * @flags: Storage for interrupt flags + * + * The function can be used in any context such as NMI or HARDIRQ. Due to + * locking constrains it will _always_ fail to acquire the lock in NMI or + * HARDIRQ context on PREEMPT_RT. + */ +#define localtry_trylock_irqsave(lock, flags) \ + __localtry_trylock_irqsave(lock, flags) + +/** + * local_unlock - Release a per CPU local lock + * @lock: The lock variable + */ +#define localtry_unlock(lock) __localtry_unlock(lock) + +/** + * local_unlock_irq - Release a per CPU local lock and enable interrupts + * @lock: The lock variable + */ +#define localtry_unlock_irq(lock) __localtry_unlock_irq(lock) + +/** + * localtry_unlock_irqrestore - Release a per CPU local lock and restore + * interrupt flags + * @lock: The lock variable + * @flags: Interrupt flags to restore + */ +#define localtry_unlock_irqrestore(lock, flags) \ + __localtry_unlock_irqrestore(lock, flags) + DEFINE_GUARD(local_lock, local_lock_t __percpu*, local_lock(_T), local_unlock(_T)) diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h index 8dd71fbbb6d2b6748969438c4642f7d970834871..67bd13d142fac39bc0f8b2c05eaf81717ff480f9 100644 --- a/include/linux/local_lock_internal.h +++ b/include/linux/local_lock_internal.h @@ -15,6 +15,11 @@ typedef struct { #endif } local_lock_t; +typedef struct { + local_lock_t llock; + unsigned int acquired; +} localtry_lock_t; + #ifdef CONFIG_DEBUG_LOCK_ALLOC # define LOCAL_LOCK_DEBUG_INIT(lockname) \ .dep_map = { \ @@ -31,6 +36,13 @@ static inline void local_lock_acquire(local_lock_t *l) l->owner = current; } +static inline void local_trylock_acquire(local_lock_t *l) +{ + lock_map_acquire_try(&l->dep_map); + DEBUG_LOCKS_WARN_ON(l->owner); + l->owner = current; +} + static inline void local_lock_release(local_lock_t *l) { DEBUG_LOCKS_WARN_ON(l->owner != current); @@ -45,11 +57,13 @@ static inline void local_lock_debug_init(local_lock_t *l) #else /* CONFIG_DEBUG_LOCK_ALLOC */ # define LOCAL_LOCK_DEBUG_INIT(lockname) static inline void local_lock_acquire(local_lock_t *l) { } +static inline void local_trylock_acquire(local_lock_t *l) { } static inline void local_lock_release(local_lock_t *l) { } static inline void local_lock_debug_init(local_lock_t *l) { } #endif /* !CONFIG_DEBUG_LOCK_ALLOC */ #define INIT_LOCAL_LOCK(lockname) { LOCAL_LOCK_DEBUG_INIT(lockname) } +#define INIT_LOCALTRY_LOCK(lockname) { .llock = { LOCAL_LOCK_DEBUG_INIT(lockname.llock) }} #define __local_lock_init(lock) \ do { \ @@ -118,6 +132,104 @@ do { \ #define __local_unlock_nested_bh(lock) \ local_lock_release(this_cpu_ptr(lock)) +/* localtry_lock_t variants */ + +#define __localtry_lock_init(lock) \ +do { \ + __local_lock_init(&(lock)->llock); \ + WRITE_ONCE((lock)->acquired, 0); \ +} while (0) + +#define __localtry_lock(lock) \ + do { \ + localtry_lock_t *lt; \ + preempt_disable(); \ + lt = this_cpu_ptr(lock); \ + local_lock_acquire(<->llock); \ + WRITE_ONCE(lt->acquired, 1); \ + } while (0) + +#define __localtry_lock_irq(lock) \ + do { \ + localtry_lock_t *lt; \ + local_irq_disable(); \ + lt = this_cpu_ptr(lock); \ + local_lock_acquire(<->llock); \ + WRITE_ONCE(lt->acquired, 1); \ + } while (0) + +#define __localtry_lock_irqsave(lock, flags) \ + do { \ + localtry_lock_t *lt; \ + local_irq_save(flags); \ + lt = this_cpu_ptr(lock); \ + local_lock_acquire(<->llock); \ + WRITE_ONCE(lt->acquired, 1); \ + } while (0) + +#define __localtry_trylock(lock) \ + ({ \ + localtry_lock_t *lt; \ + bool _ret; \ + \ + preempt_disable(); \ + lt = this_cpu_ptr(lock); \ + if (!READ_ONCE(lt->acquired)) { \ + WRITE_ONCE(lt->acquired, 1); \ + local_trylock_acquire(<->llock); \ + _ret = true; \ + } else { \ + _ret = false; \ + preempt_enable(); \ + } \ + _ret; \ + }) + +#define __localtry_trylock_irqsave(lock, flags) \ + ({ \ + localtry_lock_t *lt; \ + bool _ret; \ + \ + local_irq_save(flags); \ + lt = this_cpu_ptr(lock); \ + if (!READ_ONCE(lt->acquired)) { \ + WRITE_ONCE(lt->acquired, 1); \ + local_trylock_acquire(<->llock); \ + _ret = true; \ + } else { \ + _ret = false; \ + local_irq_restore(flags); \ + } \ + _ret; \ + }) + +#define __localtry_unlock(lock) \ + do { \ + localtry_lock_t *lt; \ + lt = this_cpu_ptr(lock); \ + WRITE_ONCE(lt->acquired, 0); \ + local_lock_release(<->llock); \ + preempt_enable(); \ + } while (0) + +#define __localtry_unlock_irq(lock) \ + do { \ + localtry_lock_t *lt; \ + lt = this_cpu_ptr(lock); \ + WRITE_ONCE(lt->acquired, 0); \ + local_lock_release(<->llock); \ + local_irq_enable(); \ + } while (0) + +#define __localtry_unlock_irqrestore(lock, flags) \ + do { \ + localtry_lock_t *lt; \ + lt = this_cpu_ptr(lock); \ + WRITE_ONCE(lt->acquired, 0); \ + local_lock_release(<->llock); \ + local_irq_restore(flags); \ + } while (0) + #else /* !CONFIG_PREEMPT_RT */ /* @@ -125,8 +237,10 @@ do { \ * critical section while staying preemptible. */ typedef spinlock_t local_lock_t; +typedef spinlock_t localtry_lock_t; #define INIT_LOCAL_LOCK(lockname) __LOCAL_SPIN_LOCK_UNLOCKED((lockname)) +#define INIT_LOCALTRY_LOCK(lockname) INIT_LOCAL_LOCK(lockname) #define __local_lock_init(l) \ do { \ @@ -169,4 +283,36 @@ do { \ spin_unlock(this_cpu_ptr((lock))); \ } while (0) +/* localtry_lock_t variants */ + +#define __localtry_lock_init(lock) __local_lock_init(lock) +#define __localtry_lock(lock) __local_lock(lock) +#define __localtry_lock_irq(lock) __local_lock(lock) +#define __localtry_lock_irqsave(lock, flags) __local_lock_irqsave(lock, flags) +#define __localtry_unlock(lock) __local_unlock(lock) +#define __localtry_unlock_irq(lock) __local_unlock(lock) +#define __localtry_unlock_irqrestore(lock, flags) __local_unlock_irqrestore(lock, flags) + +#define __localtry_trylock(lock) \ + ({ \ + int __locked; \ + \ + if (in_nmi() | in_hardirq()) { \ + __locked = 0; \ + } else { \ + migrate_disable(); \ + __locked = spin_trylock(this_cpu_ptr((lock))); \ + if (!__locked) \ + migrate_enable(); \ + } \ + __locked; \ + }) + +#define __localtry_trylock_irqsave(lock, flags) \ + ({ \ + typecheck(unsigned long, flags); \ + flags = 0; \ + __localtry_trylock(lock); \ + }) + #endif /* CONFIG_PREEMPT_RT */