Re: [PATCH 2/3] rwsem: Implement down_read_interruptible

Waiman Long
2020-12-07T15:35:47Z

On 12/7/20 4:02 AM, Peter Zijlstra wrote:
> On Thu, Dec 03, 2020 at 08:59:13PM -0500, Waiman Long wrote:
>> On 12/3/20 3:11 PM, Eric W. Biederman wrote:
>>> +static inline int __down_read_interruptible(struct rw_semaphore *sem)
>>> +{
>>> + if (!rwsem_read_trylock(sem)) {
>>> + if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE)))
>>> + return -EINTR;
>>> + DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
>>> + } else {
>>> + rwsem_set_reader_owned(sem);
>>> + }
>>> + return 0;
>>> +}
>>> +
>>> static inline int __down_read_killable(struct rw_semaphore *sem)
>>> {
>>> if (!rwsem_read_trylock(sem)) {
>>> @@ -1495,6 +1507,20 @@ void __sched down_read(struct rw_semaphore *sem)
>>> }
>>> EXPORT_SYMBOL(down_read);
>>> +int __sched down_read_interruptible(struct rw_semaphore *sem)
>>> +{
>>> + might_sleep();
>>> + rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
>>> +
>>> + if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) {
>>> + rwsem_release(&sem->dep_map, _RET_IP_);
>>> + return -EINTR;
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +EXPORT_SYMBOL(down_read_interruptible);
>>> +
>>> int __sched down_read_killable(struct rw_semaphore *sem)
>>> {
>>> might_sleep();
>> Acked-by: Waiman Long <longman@redhat.com>
> Yeah, that seems correct.. There's an unfortunate amount of copy-paste
> there though.
>
> Do we want to follow that up with something like this?

I am actually thinking about similar streamlining once the patch lands.

Your suggested changes look fine to me.

Cheers,
Longman