linux-kernel - Re: atomic read and increment question

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Message-ID: <20140318125256.GJ4420@linux.vnet.ibm.com>
Date:	Tue, 18 Mar 2014 05:52:56 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	noman pouigt <variksla@...il.com>
Cc:	rostedt@...dmis.org, rusty@...tcorp.com.au,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: Re: atomic read and increment question

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

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