Commit e4ab322f authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

cleanup: Add conditional guard support 



Adds:

 - DEFINE_GUARD_COND() / DEFINE_LOCK_GUARD_1_COND() to extend existing
   guards with conditional lock primitives, eg. mutex_trylock(),
   mutex_lock_interruptible().

   nb. both primitives allow NULL 'locks', which cause the lock to
       fail (obviously).

 - extends scoped_guard() to not take the body when the the
   conditional guard 'fails'. eg.

     scoped_guard (mutex_intr, &task->signal_cred_guard_mutex) {
	...
     }

   will only execute the body when the mutex is held.

 - provides scoped_cond_guard(name, fail, args...); which extends
   scoped_guard() to do fail when the lock-acquire fails.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231102110706.460851167%40infradead.org
parent b85ea95d

include/linux/cleanup.h

+49 −3
Original line number Diff line number Diff line
@@ -125,25 +125,55 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ 
 *	trivial wrapper around DEFINE_CLASS() above specifically

 *	for locks.

 *

 * DEFINE_GUARD_COND(name, ext, condlock)

 *	wrapper around EXTEND_CLASS above to add conditional lock

 *	variants to a base class, eg. mutex_trylock() or

 *	mutex_lock_interruptible().

 *

 * guard(name):

 *	an anonymous instance of the (guard) class

 *	an anonymous instance of the (guard) class, not recommended for

 *	conditional locks.

 *

 * scoped_guard (name, args...) { }:

 *	similar to CLASS(name, scope)(args), except the variable (with the

 *	explicit name 'scope') is declard in a for-loop such that its scope is

 *	bound to the next (compound) statement.

 *

 *	for conditional locks the loop body is skipped when the lock is not

 *	acquired.

 *

 * scoped_cond_guard (name, fail, args...) { }:

 *      similar to scoped_guard(), except it does fail when the lock

 *      acquire fails.

 *

 */



#define DEFINE_GUARD(_name, _type, _lock, _unlock) \

	DEFINE_CLASS(_name, _type, _unlock, ({ _lock; _T; }), _type _T)

	DEFINE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }), _type _T); \

	static inline void * class_##_name##_lock_ptr(class_##_name##_t *_T) \

	{ return *_T; }



#define DEFINE_GUARD_COND(_name, _ext, _condlock) \

	EXTEND_CLASS(_name, _ext, \

		     ({ void *_t = _T; if (_T && !(_condlock)) _t = NULL; _t; }), \

		     class_##_name##_t _T) \

	static inline void * class_##_name##_ext##_lock_ptr(class_##_name##_t *_T) \

	{ return class_##_name##_lock_ptr(_T); }



#define guard(_name) \

	CLASS(_name, __UNIQUE_ID(guard))



#define __guard_ptr(_name) class_##_name##_lock_ptr



#define scoped_guard(_name, args...)					\

	for (CLASS(_name, scope)(args),					\

	     *done = NULL; !done; done = (void *)1)

	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)



#define scoped_cond_guard(_name, _fail, args...) \

	for (CLASS(_name, scope)(args), \

	     *done = NULL; !done; done = (void *)1) \

		if (!__guard_ptr(_name)(&scope)) _fail; \

		else



/*

 * Additional helper macros for generating lock guards with types, either for
@@ -152,6 +182,7 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ 
 *

 * DEFINE_LOCK_GUARD_0(name, lock, unlock, ...)

 * DEFINE_LOCK_GUARD_1(name, type, lock, unlock, ...)

 * DEFINE_LOCK_GUARD_1_COND(name, ext, condlock)

 *

 * will result in the following type:

 *
@@ -173,6 +204,11 @@ typedef struct { \ 
static inline void class_##_name##_destructor(class_##_name##_t *_T)	\

{									\

	if (_T->lock) { _unlock; }					\

}									\

									\

static inline void *class_##_name##_lock_ptr(class_##_name##_t *_T)	\

{									\

	return _T->lock;						\

}
@@ -201,4 +237,14 @@ __DEFINE_LOCK_GUARD_1(_name, _type, _lock) 
__DEFINE_UNLOCK_GUARD(_name, void, _unlock, __VA_ARGS__)		\

__DEFINE_LOCK_GUARD_0(_name, _lock)



#define DEFINE_LOCK_GUARD_1_COND(_name, _ext, _condlock)		\

	EXTEND_CLASS(_name, _ext,					\

		     ({ class_##_name##_t _t = { .lock = l }, *_T = &_t;\

		        if (_T->lock && !(_condlock)) _T->lock = NULL;	\

			_t; }),						\

		     typeof_member(class_##_name##_t, lock) l)		\

	static inline void * class_##_name##_ext##_lock_ptr(class_##_name##_t *_T) \

	{ return class_##_name##_lock_ptr(_T); }





#endif /* __LINUX_GUARDS_H */

include/linux/mutex.h

+2 −1
Original line number Diff line number Diff line
@@ -221,6 +221,7 @@ extern void mutex_unlock(struct mutex *lock); 
extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);



DEFINE_GUARD(mutex, struct mutex *, mutex_lock(_T), mutex_unlock(_T))

DEFINE_FREE(mutex, struct mutex *, if (_T) mutex_unlock(_T))

DEFINE_GUARD_COND(mutex, _try, mutex_trylock(_T))

DEFINE_GUARD_COND(mutex, _intr, mutex_lock_interruptible(_T) == 0)



#endif /* __LINUX_MUTEX_H */

include/linux/rwsem.h

+4 −4
Original line number Diff line number Diff line
@@ -203,11 +203,11 @@ extern void up_read(struct rw_semaphore *sem); 
extern void up_write(struct rw_semaphore *sem);



DEFINE_GUARD(rwsem_read, struct rw_semaphore *, down_read(_T), up_read(_T))

DEFINE_GUARD(rwsem_write, struct rw_semaphore *, down_write(_T), up_write(_T))



DEFINE_FREE(up_read, struct rw_semaphore *, if (_T) up_read(_T))

DEFINE_FREE(up_write, struct rw_semaphore *, if (_T) up_write(_T))

DEFINE_GUARD_COND(rwsem_read, _try, down_read_trylock(_T))

DEFINE_GUARD_COND(rwsem_read, _intr, down_read_interruptible(_T) == 0)



DEFINE_GUARD(rwsem_write, struct rw_semaphore *, down_write(_T), up_write(_T))

DEFINE_GUARD_COND(rwsem_write, _try, down_write_trylock(_T))



/*

 * downgrade write lock to read lock

include/linux/spinlock.h

+15 −0
Original line number Diff line number Diff line
@@ -507,6 +507,8 @@ DEFINE_LOCK_GUARD_1(raw_spinlock, raw_spinlock_t, 
		    raw_spin_lock(_T->lock),

		    raw_spin_unlock(_T->lock))



DEFINE_LOCK_GUARD_1_COND(raw_spinlock, _try, raw_spin_trylock(_T->lock))



DEFINE_LOCK_GUARD_1(raw_spinlock_nested, raw_spinlock_t,

		    raw_spin_lock_nested(_T->lock, SINGLE_DEPTH_NESTING),

		    raw_spin_unlock(_T->lock))
@@ -515,23 +517,36 @@ DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t, 
		    raw_spin_lock_irq(_T->lock),

		    raw_spin_unlock_irq(_T->lock))



DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq(_T->lock))



DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,

		    raw_spin_lock_irqsave(_T->lock, _T->flags),

		    raw_spin_unlock_irqrestore(_T->lock, _T->flags),

		    unsigned long flags)



DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irqsave, _try,

			 raw_spin_trylock_irqsave(_T->lock, _T->flags))



DEFINE_LOCK_GUARD_1(spinlock, spinlock_t,

		    spin_lock(_T->lock),

		    spin_unlock(_T->lock))



DEFINE_LOCK_GUARD_1_COND(spinlock, _try, spin_trylock(_T->lock))



DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,

		    spin_lock_irq(_T->lock),

		    spin_unlock_irq(_T->lock))



DEFINE_LOCK_GUARD_1_COND(spinlock_irq, _try,

			 spin_trylock_irq(_T->lock))



DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,

		    spin_lock_irqsave(_T->lock, _T->flags),

		    spin_unlock_irqrestore(_T->lock, _T->flags),

		    unsigned long flags)



DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try,

			 spin_trylock_irqsave(_T->lock, _T->flags))



#undef __LINUX_INSIDE_SPINLOCK_H

#endif /* __LINUX_SPINLOCK_H */