From patchwork Wed Feb 12 17:47:02 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 13972251 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-pj1-f51.google.com (mail-pj1-f51.google.com [209.85.216.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F52D20F09A for ; Wed, 12 Feb 2025 17:47:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739382444; cv=none; b=nOPZvYdqjT//KwGh7eGDgF61mgqGji3+tM+7OtA+N3QRFpxjZH1Eptz3OMq2ZmuTmlDaXBg9Aahr71oXxVgQm9xLSc7AkkyABP50iO2v3WN8baJ9FRcIARJEii3xsjUL3yj+YZyG58p8w0IMqiCHeNk0dwzNNPMDC2/Bid91qkc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739382444; c=relaxed/simple; bh=U90v5Pk93VeiqRlGaWd3w3TfoItyJk0Pr1aSpT1G4VI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=u73ZhNn7XHB+zXq7fz7kdwKfwes06zp1OHObGM8AQyeQh73Z2ZQTV/g0e9/mdU83nhzGWycghO3L6u3pRzU4m432FW7nQrRQPYJrXSRg9EQv/FnjlkgpLa2DBrh4q7oAqkoeKwGOSKzbetCVUVVKp5G14gF4z3s7S3qVOS/+1vU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=NUfWEvd9; arc=none smtp.client-ip=209.85.216.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="NUfWEvd9" Received: by mail-pj1-f51.google.com with SMTP id 98e67ed59e1d1-2f833af7a09so62913a91.2 for ; Wed, 12 Feb 2025 09:47:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1739382442; x=1739987242; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Dxu1Rc7/sI72JB4NYxxk9elaSjOiJ9Td89bVV/zMYyc=; b=NUfWEvd9I/BwfrNrsNRizS1dd6sYvY3R/PAumgzHPgUWZfCRqgj1uq3Xdz5j3gIYBo DjVl2a3yn4v2o97TW/qC5HxHcExDdXID00O7qBNVodI+lJObsJsqjnnITseN0IQDK4d4 UOSKpl5nZpu4QkGHsKm3jgS6R7mvaEV8ykMdyjYAokzfVEhek28c4A8t7lZjIKpPLitR zEzXLOpIvX2ejGPNjPX3XWQbiyHza/Z200auOPCYKlLglbi1BgxneewZZcr4A87xh4DB 5fOS9/AQ7yeaI3i3VrCVh1JyQm4zhI8MMyBki6zKEo3MF9lWEkjfh2XVBE3GhNHE600r 3UKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739382442; x=1739987242; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Dxu1Rc7/sI72JB4NYxxk9elaSjOiJ9Td89bVV/zMYyc=; b=Fam220VK4yd+pSM7iU7hRQwyEq+t1b23idF6mO9ACyyToD2RxA6+hPx2HpEjyLp33K G/EmeCxwJ7fWNCDd7sHpH/2OcmgO4Jf/2DwR+s7RVxXx1aPYawivRXdtZbYu/dt9Ur7U 3ZEd2Nv8eSIXu52c81z6Ho5dDAepHFrBAV0xqQwL+6OWlnuISXqnP7uVNjiZBGIH8Mbq l7CQKRc2OOA9t7O0lyarDWAgRdqAUQVzL5OBSHLIBIjuPpNfjdmKP6AfToqZqA9QnoVh oJIyzLk6cCU+ESUncaJalfOL70/FHQR1LofwNK9O9rQLmVGqaATncpln9D0z8a7wZ4wT CKcQ== X-Gm-Message-State: AOJu0YwIMSRLMiiuixEFnLUiY2WLsgDuvDqZuFCBWNwLOUKB4DR9tAqZ 5A4/aUffkf4NZLhuPWfx3E97YwXPyGjOU8D7YAZHsH7eCYEeaS3ddWb40Q== X-Gm-Gg: ASbGncscWAhcdl5M4mT3cWToysWrobqgIAi3u/4syrxM+Z1LkvnpPIooope0YDxLUdw kvs9nTDVejDERTae+Q5oNzR8xJyrpXbFdgDyVT5dUgjgwJ1b2cwha2UEukfFscgdPNoVn+UL8O1 0TTzaYc6jYJ7qV3qSKynXLJ2gf5Y7JBGaWIPEQ/p+9U4aM51ZJgEnYMqD32hWdNO4d8xhokTN9D q2u6V5tK0sWw6SzXqjXudT6ikzJJvjcEqfzAgtqzIaop7tUJLdJ1mcpfduhSt8uMuopz3wQ4wYV zQkyt8xcUxEDIEJajJoozXSEnvab+qmEhelEER7XHN1kWg== X-Google-Smtp-Source: AGHT+IFdzeREzMu6Nvpg1XZZgAM871rh2ju2mt7o2mzuvJjED9/Nt9+adPMlY6ggnat49bQIcDjxPQ== X-Received: by 2002:a17:90a:d00e:b0:2ee:d433:7c50 with SMTP id 98e67ed59e1d1-2fbf5c5a06dmr4937863a91.23.1739382441983; Wed, 12 Feb 2025 09:47:21 -0800 (PST) Received: from ast-mac.thefacebook.com ([2620:10d:c090:500::4:c330]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2fbf9908835sm1805194a91.42.2025.02.12.09.47.20 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 12 Feb 2025 09:47:21 -0800 (PST) From: Alexei Starovoitov To: bpf@vger.kernel.org Cc: andrii@kernel.org, memxor@gmail.com, akpm@linux-foundation.org, peterz@infradead.org, vbabka@suse.cz, bigeasy@linutronix.de, rostedt@goodmis.org, houtao1@huawei.com, hannes@cmpxchg.org, mhocko@suse.com, willy@infradead.org, tglx@linutronix.de, jannh@google.com, tj@kernel.org, linux-mm@kvack.org, kernel-team@fb.com Subject: [PATCH bpf-next v7 3/6] locking/local_lock: Introduce localtry_lock_t Date: Wed, 12 Feb 2025 09:47:02 -0800 Message-Id: <20250212174705.44492-4-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20250212174705.44492-1-alexei.starovoitov@gmail.com> References: <20250212174705.44492-1-alexei.starovoitov@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net 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 --- 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 091dc0b6bdfb..05c254a5d7d3 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 8dd71fbbb6d2..c1369b300777 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 */