Re: [patch] Re: using long instead of atomic_t when only set/read is required

Nick Piggin
2008-03-03T17:34:48Z

On Tuesday 04 March 2008 02:53, Alan Cox wrote:
> > Atomicity of reads of write for pointers and integral types (other than
> > long long) should be documented.
>
> NAK.
>
> Atomicity of reads or writes for pointers and integral types is NOT
> guaranteed. Gcc doesn't believe in your guarantee.

Are you sure gcc doesn't? Or is it just "C"?

Linux wouldn't work today if gcc did something non-atomic there
(presuming you're talking about naturally aligned pointers/ints).
It is widely used and accepted.

RCU users are far from the only places to rely on this, although
I guess they are the main ones when it comes to assigning pointers
atomically.