Re: [PATCH] kernel: fix data race in put_pid

Peter Zijlstra
2015-09-18T09:39:24Z

On Fri, Sep 18, 2015 at 10:28:20AM +0100, Will Deacon wrote:
> > #define atomic_read_ctrl(v) READ_ONCE_CTRL(&(v)->counter)
>
> Funnily enough, I had this exact same discussion off-list yesterday
> afternoon, since I wrote some code relying on a ctrl dependency from
> an atomic_read to an atomic_xchg_relaxed.
>
> So I guess I'm for the addition, but at the same time, could we make
> atomic_read and atomic_set generic too?

Nope (having just gone through them), there's a few archs that implement
them in asm or even outright function calls (see blackfin, metag,
powerpc, s390).

That said, the patch I just send should see them all be at least
{READ,WRITE}_ONCE, the asm one obviously qualify for that etc..