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Fri, 14 Feb 2025 16:27:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id qMYyIv5ur2eHSAAAD6G6ig (envelope-from ); Fri, 14 Feb 2025 16:27:42 +0000 From: Vlastimil Babka Date: Fri, 14 Feb 2025 17:27:39 +0100 Subject: [PATCH RFC v2 03/10] locking/local_lock: Introduce localtry_lock_t MIME-Version: 1.0 Message-Id: <20250214-slub-percpu-caches-v2-3-88592ee0966a@suse.cz> References: <20250214-slub-percpu-caches-v2-0-88592ee0966a@suse.cz> In-Reply-To: <20250214-slub-percpu-caches-v2-0-88592ee0966a@suse.cz> To: Suren Baghdasaryan , "Liam R. Howlett" , Christoph Lameter , David Rientjes Cc: Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org, Sebastian Andrzej Siewior , Alexei Starovoitov , Vlastimil Babka X-Mailer: b4 0.14.2 X-Rspamd-Queue-Id: 172051C000F X-Stat-Signature: spje6ybkk8o7yepcjk4cg4mk17yis64n X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1739550470-675287 X-HE-Meta: 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 oY6CE5re E+dpNfNIiwMyfGAszOcYdNT6/BedtuoORwAycSF9On45iRirZ7pLns+M/e3XIJ8TZO0oVvGLu296cXd9fOCwW7cSJDa4CcV5byA3mb+xa2Xdum7v29jLdkxIg5/Lz29wxtqZHnOpPOdjgpQeNSzLeAG3yOksntL4nlFt+m/uWJkDH8PXzYh4aFR1uSyaZJ8tuVeMP3jsBFqYYbndzrPf5zbfjCnwRj6O9WgU8xcn9mKvKrPGJJdY+diuD+jOu2p0ly3TzJcFPjFtbwMJIUuDJnLFs20vZu++AlB7ZsnvHWNcz7TCS4tQk+wjXh16WPXK9NFCLixcLrTM1uTGEMsmPHJt5vUqYJcGVLfbKiMWDMUu14VUnSufeEkr7OwD7R0Jq5vMlZpYQSKswIbU= 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 PI issues. Note there is no need to use local_inc for acquired variable, since it's a percpu variable with strict nesting scopes. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Alexei Starovoitov Signed-off-by: Vlastimil Babka --- include/linux/local_lock.h | 59 +++++++++++++++++ include/linux/local_lock_internal.h | 123 ++++++++++++++++++++++++++++++++++++ 2 files changed, 182 insertions(+) diff --git a/include/linux/local_lock.h b/include/linux/local_lock.h index 091dc0b6bdfb9f4721f94d19828a38fbfa59346c..05c254a5d7d3e6db64d7f81a3a4a10f5a942c29e 100644 --- a/include/linux/local_lock.h +++ b/include/linux/local_lock.h @@ -51,6 +51,65 @@ #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_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 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..c1369b300777d3ff3700cfd8bd4de8186124f036 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 +132,86 @@ 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_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 +219,10 @@ 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 +265,31 @@ 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_irqsave(lock, flags) \ + ({ \ + int __locked; \ + \ + typecheck(unsigned long, flags); \ + flags = 0; \ + if (in_nmi() | in_hardirq()) { \ + __locked = 0; \ + } else { \ + migrate_disable(); \ + __locked = spin_trylock(this_cpu_ptr((lock))); \ + if (!__locked) \ + migrate_enable(); \ + } \ + __locked; \ + }) + #endif /* CONFIG_PREEMPT_RT */