[tip:,locking/core] locking/rwsem: Disable preemption in all down_write*() and up_write() code paths
Commit Message
The following commit has been merged into the locking/core branch of tip:
Commit-ID: 1d61659ced6bd8881cf2fb5cbcb28f9541fc7430
Gitweb: https://git.kernel.org/tip/1d61659ced6bd8881cf2fb5cbcb28f9541fc7430
Author: Waiman Long <longman@redhat.com>
AuthorDate: Wed, 25 Jan 2023 19:36:27 -05:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 26 Jan 2023 11:46:46 +01:00
locking/rwsem: Disable preemption in all down_write*() and up_write() code paths
The previous patch has disabled preemption in all the down_read() and
up_read() code paths. For symmetry, this patch extends commit:
48dfb5d2560d ("locking/rwsem: Disable preemption while trying for rwsem lock")
... to have preemption disabled in all the down_write() and up_write()
code paths, including downgrade_write().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230126003628.365092-4-longman@redhat.com
---
kernel/locking/rwsem.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)
@@ -256,16 +256,13 @@ static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
static inline bool rwsem_write_trylock(struct rw_semaphore *sem)
{
long tmp = RWSEM_UNLOCKED_VALUE;
- bool ret = false;
- preempt_disable();
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, RWSEM_WRITER_LOCKED)) {
rwsem_set_owner(sem);
- ret = true;
+ return true;
}
- preempt_enable();
- return ret;
+ return false;
}
/*
@@ -716,7 +713,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
return false;
}
- preempt_disable();
/*
* Disable preemption is equal to the RCU read-side crital section,
* thus the task_strcut structure won't go away.
@@ -728,7 +724,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
if ((flags & RWSEM_NONSPINNABLE) ||
(owner && !(flags & RWSEM_READER_OWNED) && !owner_on_cpu(owner)))
ret = false;
- preempt_enable();
lockevent_cond_inc(rwsem_opt_fail, !ret);
return ret;
@@ -828,8 +823,6 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
int loop = 0;
u64 rspin_threshold = 0;
- preempt_disable();
-
/* sem->wait_lock should not be held when doing optimistic spinning */
if (!osq_lock(&sem->osq))
goto done;
@@ -937,7 +930,6 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
}
osq_unlock(&sem->osq);
done:
- preempt_enable();
lockevent_cond_inc(rwsem_opt_fail, !taken);
return taken;
}
@@ -1178,15 +1170,12 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
if (waiter.handoff_set) {
enum owner_state owner_state;
- preempt_disable();
owner_state = rwsem_spin_on_owner(sem);
- preempt_enable();
-
if (owner_state == OWNER_NULL)
goto trylock_again;
}
- schedule();
+ schedule_preempt_disabled();
lockevent_inc(rwsem_sleep_writer);
set_current_state(state);
trylock_again:
@@ -1310,12 +1299,15 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
*/
static inline int __down_write_common(struct rw_semaphore *sem, int state)
{
+ int ret = 0;
+
+ preempt_disable();
if (unlikely(!rwsem_write_trylock(sem))) {
if (IS_ERR(rwsem_down_write_slowpath(sem, state)))
- return -EINTR;
+ ret = -EINTR;
}
-
- return 0;
+ preempt_enable();
+ return ret;
}
static inline void __down_write(struct rw_semaphore *sem)
@@ -1330,8 +1322,14 @@ static inline int __down_write_killable(struct rw_semaphore *sem)
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
+ int ret;
+
+ preempt_disable();
DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
- return rwsem_write_trylock(sem);
+ ret = rwsem_write_trylock(sem);
+ preempt_enable();
+
+ return ret;
}
/*
@@ -1374,9 +1372,9 @@ static inline void __up_write(struct rw_semaphore *sem)
preempt_disable();
rwsem_clear_owner(sem);
tmp = atomic_long_fetch_add_release(-RWSEM_WRITER_LOCKED, &sem->count);
- preempt_enable();
if (unlikely(tmp & RWSEM_FLAG_WAITERS))
rwsem_wake(sem);
+ preempt_enable();
}
/*
@@ -1394,11 +1392,13 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
* write side. As such, rely on RELEASE semantics.
*/
DEBUG_RWSEMS_WARN_ON(rwsem_owner(sem) != current, sem);
+ preempt_disable();
tmp = atomic_long_fetch_add_release(
-RWSEM_WRITER_LOCKED+RWSEM_READER_BIAS, &sem->count);
rwsem_set_reader_owned(sem);
if (tmp & RWSEM_FLAG_WAITERS)
rwsem_downgrade_wake(sem);
+ preempt_enable();
}
#else /* !CONFIG_PREEMPT_RT */