atomic read and increment question

atomic read and increment question

[noman pouigt]

Hello,

I looked through the documentation for atomic
operations but couldn't find out the api for following
operation:

x = 1;
temp = atomic_read_increment(x);

so basically this will read the old value of x in temp
and then increment x.

so temp = 1 and x = 2.

Is this api already available?

Thanks,

Re: atomic read and increment question

[Clemens Ladisch]

noman pouigt wrote:
> x = 1;
> temp = atomic_read_increment(x);

atomic_set(&x, 1);
temp = atomic_inc_return(&x);

> I looked through the documentation for atomic
> operations but couldn't find out the api

Not everything is fully documented.

Look through include/asm-generic/atomic.h.


Regards,
Clemens

Re: atomic read and increment question

[Paul E. McKenney]

On Tue, Mar 18, 2014 at 01:26:12AM -0700, noman pouigt wrote:
> Hello,
> 
> I looked through the documentation for atomic
> operations but couldn't find out the api for following
> operation:
> 
> x = 1;
> temp = atomic_read_increment(x);
> 
> so basically this will read the old value of x in temp
> and then increment x.
> 
> so temp = 1 and x = 2.
> 
> Is this api already available?

You want atomic_inc_return().  It returns the new value rather than the
old value, but you can do the following:

	temp = atomic_inc_return(&x) - 1;

							Thanx, Paul