Re: atomic use is not atomic?

[Lars-Peter Clausen <lars@metafoo.de>]

On 6/8/21 2:35 PM, Andy Shevchenko wrote:
> Hi!
>
> Can anybody explain this code [1] in terms of atomicity?
>
>    if (!atomic_read(&trig->use_count)) {
>      atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
>      ...
>    }
>
> AFAIU how atomics are supposed to work the above doesn't do anything
> atomically. I.o.w. use_count may be simple int with the same effect.
>
The operations here do not require atomic access, it is just operating 
on a atomic type. The atomic access is the atomic_dec_and_test() in 
iio_trigger_notify_done().