diff options
| author | Waiman Long <longman@redhat.com> | 2020-11-21 07:14:12 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-12-09 19:08:47 +0300 |
| commit | c8fe8b0564388f41147326f31e4587171aacccd4 (patch) | |
| tree | da3fb2f70ad4d542f0260c8115842bb97e651a65 | |
| parent | c995e638ccbbc65a76d1713c4fdcf927e7e2cb83 (diff) | |
| download | linux-c8fe8b0564388f41147326f31e4587171aacccd4.tar.xz | |
locking/rwsem: Pass the current atomic count to rwsem_down_read_slowpath()
The atomic count value right after reader count increment can be useful
to determine the rwsem state at trylock time. So the count value is
passed down to rwsem_down_read_slowpath() to be used when appropriate.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Link: https://lkml.kernel.org/r/20201121041416.12285-2-longman@redhat.com
| -rw-r--r-- | kernel/locking/rwsem.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 67ae366d08dd..5768b90223c0 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -270,14 +270,14 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem) owner | RWSEM_NONSPINNABLE)); } -static inline bool rwsem_read_trylock(struct rw_semaphore *sem) +static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp) { - long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count); + *cntp = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count); - if (WARN_ON_ONCE(cnt < 0)) + if (WARN_ON_ONCE(*cntp < 0)) rwsem_set_nonspinnable(sem); - if (!(cnt & RWSEM_READ_FAILED_MASK)) { + if (!(*cntp & RWSEM_READ_FAILED_MASK)) { rwsem_set_reader_owned(sem); return true; } @@ -1008,9 +1008,9 @@ rwsem_spin_on_owner(struct rw_semaphore *sem, unsigned long nonspinnable) * Wait for the read lock to be granted */ static struct rw_semaphore __sched * -rwsem_down_read_slowpath(struct rw_semaphore *sem, int state) +rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, int state) { - long count, adjustment = -RWSEM_READER_BIAS; + long adjustment = -RWSEM_READER_BIAS; struct rwsem_waiter waiter; DEFINE_WAKE_Q(wake_q); bool wake = false; @@ -1356,8 +1356,10 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem) */ static inline int __down_read_common(struct rw_semaphore *sem, int state) { - if (!rwsem_read_trylock(sem)) { - if (IS_ERR(rwsem_down_read_slowpath(sem, state))) + long count; + + if (!rwsem_read_trylock(sem, &count)) { + if (IS_ERR(rwsem_down_read_slowpath(sem, count, state))) return -EINTR; DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); } |