On 1/22/20 9:20 AM, Jann Horn wrote:
> On Wed, Jan 22, 2020 at 5:02 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>> Also make it available outside of epoll, along with the helper that
>> decides if we need to copy the passed in epoll_event.
> [...]
>> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
>> index cd848e8d08e2..162af749ea50 100644
>> --- a/fs/eventpoll.c
>> +++ b/fs/eventpoll.c
> [...]
>> -static int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds)
>> +static inline int epoll_mutex_lock(struct mutex *mutex, int depth,
>> + bool nonblock)
>> +{
>> + if (!nonblock) {
>> + mutex_lock_nested(mutex, depth);
>> + return 0;
>> + }
>> + if (!mutex_trylock(mutex))
>> + return 0;
>> + return -EAGAIN;
>
> The documentation for mutex_trylock() says:
>
> * Try to acquire the mutex atomically. Returns 1 if the mutex
> * has been acquired successfully, and 0 on contention.
>
> So in the success case, this evaluates to:
>
> if (!1)
> return 0;
> return -EAGAIN;
>
> which is
>
> if (0)
> return 0;
> return -EAGAIN;
>
> which is
>
> return -EAGAIN;
>
> I think you'll have to get rid of the negation.
Doh indeed. I'll rework and run the test case, just rebased this and I
think I inadvertently used an older version. Ditto for the below.
--
Jens Axboe
