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

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

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20220829124719.675715-11-elver@google.com
This commit is contained in:
Marco Elver 2022-08-29 14:47:15 +02:00 committed by Peter Zijlstra
parent f95e5a3d59
commit 01fe8a3f81
2 changed files with 12 additions and 0 deletions
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6
include/linux/percpu-rwsem.h
View File

@ -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 *);

6
kernel/locking/percpu-rwsem.c
View File

@ -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