Commit 01fe8a3f authored by Marco Elver's avatar Marco Elver Committed by Peter Zijlstra
Browse files

locking/percpu-rwsem: Add percpu_is_write_locked() and percpu_is_read_locked() 



Implement simple accessors to probe percpu-rwsem's locked state:
percpu_is_write_locked(), percpu_is_read_locked().

Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Acked-by: default avatarIan Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20220829124719.675715-11-elver@google.com
parent f95e5a3d

include/linux/percpu-rwsem.h

+6 −0
Original line number Diff line number Diff line
@@ -121,9 +121,15 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem) 
	preempt_enable();

}



extern bool percpu_is_read_locked(struct percpu_rw_semaphore *);

extern void percpu_down_write(struct percpu_rw_semaphore *);

extern void percpu_up_write(struct percpu_rw_semaphore *);



static inline bool percpu_is_write_locked(struct percpu_rw_semaphore *sem)

{

	return atomic_read(&sem->block);

}



extern int __percpu_init_rwsem(struct percpu_rw_semaphore *,

				const char *, struct lock_class_key *);

kernel/locking/percpu-rwsem.c

+6 −0
Original line number Diff line number Diff line
@@ -192,6 +192,12 @@ EXPORT_SYMBOL_GPL(__percpu_down_read); 
	__sum;								\

})



bool percpu_is_read_locked(struct percpu_rw_semaphore *sem)

{

	return per_cpu_sum(*sem->read_count) != 0 && !atomic_read(&sem->block);

}

EXPORT_SYMBOL_GPL(percpu_is_read_locked);



/*

 * Return true if the modular sum of the sem->read_count per-CPU variable is

 * zero.  If this sum is zero, then it is stable due to the fact that if any