Files
linux-stable-mirror/include/linux/spinlock_api_up.h
T
Boqun Feng e901c1510e irq,spin_lock: Add counted interrupt disabling/enabling
Currently the nested interrupt disabling and enabling is represented by
_irqsave() and _irqrestore() APIs, which are relatively unsafe, for
example:

	<interrupts are enabled as beginning>
	spin_lock_irqsave(l1, flag1);
	spin_lock_irqsave(l2, flag2);
	spin_unlock_irqrestore(l1, flags1);
	<l2 is still held but interrupts are enabled>
	// accesses to interrupt-disable protected data will cause races

This is even easier to trigger with guard facilities:

	unsigned long flag2;

	scoped_guard(spin_lock_irqsave, l1) {
		spin_lock_irqsave(l2, flag2);
	}
	// l2 locked but interrupts are enabled.
	spin_unlock_irqrestore(l2, flag2);

(Hand-to-hand locking critical sections are not uncommon for a
fine-grained lock design)

And because of this unsafety, Rust cannot easily wrap the
interrupt-disabling locks in a safe API, which complicates the design.

To resolve this, introduce a new set of interrupt disabling APIs:

*	local_interrupt_disable();
*	local_interrupt_enable();

They work like local_irq_save() and local_irq_restore() except that 1)
the outermost local_interrupt_disable() call saves the interrupt state
into a per-CPU variable, so that the outermost local_interrupt_enable()
can restore the state, and 2) a per-CPU counter is added to record the
nest level of these calls, so that interrupts are not accidentally
enabled inside the outermost critical section.

Also add the corresponding spin_lock primitives: spin_lock_irq_disable()
and spin_unlock_irq_enable(), as a result, code as follows:

	spin_lock_irq_disable(l1);
	spin_lock_irq_disable(l2);
	spin_unlock_irq_enable(l1);
	// Interrupts are still disabled.
	spin_unlock_irq_enable(l2);

doesn't have the issue that interrupts are accidentally enabled.

This also makes the wrapper of interrupt-disabling locks on Rust easier
to design.

[boqun: Apply Peter's feedback and fix spell errors reported by Ingo]
[boqun: Address the duplicate spin_acquire() spotted by sashiko]
Co-developed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Boqun Feng <boqun@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260804182657.87716-1-boqun@kernel.org
2026-08-10 10:50:18 +02:00

160 lines
5.0 KiB
C

#ifndef __LINUX_SPINLOCK_API_UP_H
#define __LINUX_SPINLOCK_API_UP_H
#ifndef __LINUX_INSIDE_SPINLOCK_H
# error "please don't include this file directly"
#endif
/*
* include/linux/spinlock_api_up.h
*
* spinlock API implementation on UP-nondebug (inlined implementation)
*
* portions Copyright 2005, Red Hat, Inc., Ingo Molnar
* Released under the General Public License (GPL).
*/
#define in_lock_functions(ADDR) 0
#define assert_raw_spin_locked(lock) do { (void)(lock); } while (0)
/*
* In the UP-nondebug case there's no real locking going on, so the
* only thing we have to do is to keep the preempt counts and irq
* flags straight, to suppress compiler warnings of unused lock
* variables, and to add the proper checker annotations:
*/
#define ___LOCK_(lock) \
do { __acquire(lock); (void)(lock); } while (0)
#define ___LOCK_shared(lock) \
do { __acquire_shared(lock); (void)(lock); } while (0)
#define __LOCK(lock, ...) \
do { preempt_disable(); ___LOCK_##__VA_ARGS__(lock); } while (0)
#define __LOCK_BH(lock, ...) \
do { __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); ___LOCK_##__VA_ARGS__(lock); } while (0)
#define __LOCK_IRQ(lock, ...) \
do { local_irq_disable(); __LOCK(lock, ##__VA_ARGS__); } while (0)
#define __LOCK_IRQSAVE(lock, flags, ...) \
do { local_irq_save(flags); __LOCK(lock, ##__VA_ARGS__); } while (0)
#define __LOCK_IRQ_DISABLE(lock, ...) \
do { local_interrupt_disable(); __LOCK(lock, ##__VA_ARGS__); } while (0)
#define ___UNLOCK_(lock) \
do { __release(lock); (void)(lock); } while (0)
#define ___UNLOCK_shared(lock) \
do { __release_shared(lock); (void)(lock); } while (0)
#define __UNLOCK(lock, ...) \
do { preempt_enable(); ___UNLOCK_##__VA_ARGS__(lock); } while (0)
#define __UNLOCK_BH(lock, ...) \
do { __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); \
___UNLOCK_##__VA_ARGS__(lock); } while (0)
#define __UNLOCK_IRQ(lock, ...) \
do { local_irq_enable(); __UNLOCK(lock, ##__VA_ARGS__); } while (0)
#define __UNLOCK_IRQRESTORE(lock, flags, ...) \
do { local_irq_restore(flags); __UNLOCK(lock, ##__VA_ARGS__); } while (0)
#define __UNLOCK_IRQ_ENABLE(lock, ...) \
do { __UNLOCK(lock, ##__VA_ARGS__); local_interrupt_enable(); } while (0)
#define _raw_spin_lock(lock) __LOCK(lock)
#define _raw_spin_lock_nested(lock, subclass) __LOCK(lock)
#define _raw_read_lock(lock) __LOCK(lock, shared)
#define _raw_write_lock(lock) __LOCK(lock)
#define _raw_write_lock_nested(lock, subclass) __LOCK(lock)
#define _raw_spin_lock_bh(lock) __LOCK_BH(lock)
#define _raw_read_lock_bh(lock) __LOCK_BH(lock, shared)
#define _raw_write_lock_bh(lock) __LOCK_BH(lock)
#define _raw_spin_lock_irq(lock) __LOCK_IRQ(lock)
#define _raw_spin_lock_irq_disable(lock) __LOCK_IRQ_DISABLE(lock)
#define _raw_read_lock_irq(lock) __LOCK_IRQ(lock, shared)
#define _raw_write_lock_irq(lock) __LOCK_IRQ(lock)
#define _raw_spin_lock_irqsave(lock, flags) __LOCK_IRQSAVE(lock, flags)
#define _raw_read_lock_irqsave(lock, flags) __LOCK_IRQSAVE(lock, flags, shared)
#define _raw_write_lock_irqsave(lock, flags) __LOCK_IRQSAVE(lock, flags)
static __always_inline int _raw_spin_trylock(raw_spinlock_t *lock)
__cond_acquires(true, lock)
{
__LOCK(lock);
return 1;
}
static __always_inline int _raw_spin_trylock_bh(raw_spinlock_t *lock)
__cond_acquires(true, lock)
{
__LOCK_BH(lock);
return 1;
}
static __always_inline int _raw_spin_trylock_irq(raw_spinlock_t *lock)
__cond_acquires(true, lock)
{
__LOCK_IRQ(lock);
return 1;
}
static __always_inline int _raw_spin_trylock_irq_disable(raw_spinlock_t *lock)
__cond_acquires(true, lock)
{
__LOCK_IRQ_DISABLE(lock);
return 1;
}
static __always_inline int _raw_spin_trylock_irqsave(raw_spinlock_t *lock, unsigned long *flags)
__cond_acquires(true, lock)
{
__LOCK_IRQSAVE(lock, *(flags));
return 1;
}
static __always_inline int _raw_read_trylock(rwlock_t *lock)
__cond_acquires_shared(true, lock)
{
__LOCK(lock, shared);
return 1;
}
static __always_inline int _raw_write_trylock(rwlock_t *lock)
__cond_acquires(true, lock)
{
__LOCK(lock);
return 1;
}
static __always_inline int _raw_write_trylock_irqsave(rwlock_t *lock, unsigned long *flags)
__cond_acquires(true, lock)
{
__LOCK_IRQSAVE(lock, *(flags));
return 1;
}
#define _raw_spin_unlock(lock) __UNLOCK(lock)
#define _raw_read_unlock(lock) __UNLOCK(lock, shared)
#define _raw_write_unlock(lock) __UNLOCK(lock)
#define _raw_spin_unlock_bh(lock) __UNLOCK_BH(lock)
#define _raw_write_unlock_bh(lock) __UNLOCK_BH(lock)
#define _raw_read_unlock_bh(lock) __UNLOCK_BH(lock, shared)
#define _raw_spin_unlock_irq(lock) __UNLOCK_IRQ(lock)
#define _raw_spin_unlock_irq_enable(lock) __UNLOCK_IRQ_ENABLE(lock)
#define _raw_read_unlock_irq(lock) __UNLOCK_IRQ(lock, shared)
#define _raw_write_unlock_irq(lock) __UNLOCK_IRQ(lock)
#define _raw_spin_unlock_irqrestore(lock, flags) \
__UNLOCK_IRQRESTORE(lock, flags)
#define _raw_read_unlock_irqrestore(lock, flags) \
__UNLOCK_IRQRESTORE(lock, flags, shared)
#define _raw_write_unlock_irqrestore(lock, flags) \
__UNLOCK_IRQRESTORE(lock, flags)
#endif /* __LINUX_SPINLOCK_API_UP_H */