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0aaddfb068
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 <dave@stgolabs.net> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Link: https://lore.kernel.org/r/20250222024427.30294-2-alexei.starovoitov@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
146 lines
4.0 KiB
C
146 lines
4.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_LOCAL_LOCK_H
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#define _LINUX_LOCAL_LOCK_H
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#include <linux/local_lock_internal.h>
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/**
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* local_lock_init - Runtime initialize a lock instance
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*/
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#define local_lock_init(lock) __local_lock_init(lock)
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/**
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* local_lock - Acquire a per CPU local lock
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* @lock: The lock variable
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*/
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#define local_lock(lock) __local_lock(lock)
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/**
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* local_lock_irq - Acquire a per CPU local lock and disable interrupts
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* @lock: The lock variable
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*/
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#define local_lock_irq(lock) __local_lock_irq(lock)
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/**
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* local_lock_irqsave - Acquire a per CPU local lock, save and disable
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* interrupts
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* @lock: The lock variable
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* @flags: Storage for interrupt flags
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*/
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#define local_lock_irqsave(lock, flags) \
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__local_lock_irqsave(lock, flags)
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/**
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* local_unlock - Release a per CPU local lock
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* @lock: The lock variable
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*/
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#define local_unlock(lock) __local_unlock(lock)
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/**
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* local_unlock_irq - Release a per CPU local lock and enable interrupts
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* @lock: The lock variable
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*/
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#define local_unlock_irq(lock) __local_unlock_irq(lock)
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/**
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* local_unlock_irqrestore - Release a per CPU local lock and restore
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* interrupt flags
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* @lock: The lock variable
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* @flags: Interrupt flags to restore
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*/
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#define local_unlock_irqrestore(lock, flags) \
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__local_unlock_irqrestore(lock, flags)
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/**
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* localtry_lock_init - Runtime initialize a lock instance
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*/
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#define localtry_lock_init(lock) __localtry_lock_init(lock)
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/**
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* localtry_lock - Acquire a per CPU local lock
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* @lock: The lock variable
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*/
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#define localtry_lock(lock) __localtry_lock(lock)
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/**
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* localtry_lock_irq - Acquire a per CPU local lock and disable interrupts
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* @lock: The lock variable
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*/
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#define localtry_lock_irq(lock) __localtry_lock_irq(lock)
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/**
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* localtry_lock_irqsave - Acquire a per CPU local lock, save and disable
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* interrupts
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* @lock: The lock variable
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* @flags: Storage for interrupt flags
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*/
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#define localtry_lock_irqsave(lock, flags) \
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__localtry_lock_irqsave(lock, flags)
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/**
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* localtry_trylock - Try to acquire a per CPU local lock.
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* @lock: The lock variable
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*
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* The function can be used in any context such as NMI or HARDIRQ. Due to
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* locking constrains it will _always_ fail to acquire the lock in NMI or
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* HARDIRQ context on PREEMPT_RT.
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*/
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#define localtry_trylock(lock) __localtry_trylock(lock)
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/**
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* localtry_trylock_irqsave - Try to acquire a per CPU local lock, save and disable
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* interrupts if acquired
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* @lock: The lock variable
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* @flags: Storage for interrupt flags
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*
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* The function can be used in any context such as NMI or HARDIRQ. Due to
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* locking constrains it will _always_ fail to acquire the lock in NMI or
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* HARDIRQ context on PREEMPT_RT.
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*/
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#define localtry_trylock_irqsave(lock, flags) \
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__localtry_trylock_irqsave(lock, flags)
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/**
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* local_unlock - Release a per CPU local lock
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* @lock: The lock variable
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*/
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#define localtry_unlock(lock) __localtry_unlock(lock)
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/**
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* local_unlock_irq - Release a per CPU local lock and enable interrupts
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* @lock: The lock variable
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*/
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#define localtry_unlock_irq(lock) __localtry_unlock_irq(lock)
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/**
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* localtry_unlock_irqrestore - Release a per CPU local lock and restore
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* interrupt flags
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* @lock: The lock variable
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* @flags: Interrupt flags to restore
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*/
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#define localtry_unlock_irqrestore(lock, flags) \
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__localtry_unlock_irqrestore(lock, flags)
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DEFINE_GUARD(local_lock, local_lock_t __percpu*,
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local_lock(_T),
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local_unlock(_T))
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DEFINE_GUARD(local_lock_irq, local_lock_t __percpu*,
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local_lock_irq(_T),
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local_unlock_irq(_T))
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DEFINE_LOCK_GUARD_1(local_lock_irqsave, local_lock_t __percpu,
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local_lock_irqsave(_T->lock, _T->flags),
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local_unlock_irqrestore(_T->lock, _T->flags),
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unsigned long flags)
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#define local_lock_nested_bh(_lock) \
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__local_lock_nested_bh(_lock)
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#define local_unlock_nested_bh(_lock) \
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__local_unlock_nested_bh(_lock)
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DEFINE_GUARD(local_lock_nested_bh, local_lock_t __percpu*,
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local_lock_nested_bh(_T),
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local_unlock_nested_bh(_T))
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#endif
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