Messages in this thread | | | Date | Thu, 19 May 2016 06:43:31 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH v2] locking/rwsem: Add reader-owned state to the owner field |
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On Thu, May 19, 2016 at 11:00:13AM +0200, Peter Zijlstra wrote: > On Wed, May 18, 2016 at 10:26:06AM -0700, Paul E. McKenney wrote: > > On Wed, May 18, 2016 at 01:05:55PM +0200, Peter Zijlstra wrote: > > > > Alternatively, could we try and talk to our GCC friends to make sure GCC > > > doesn't tear loads/stores irrespective of what the C language spec > > > allows? > > > > Interestingly enough, they used to make that guarantee, but removed it > > when C11 showed up. > > Did someone tell them this was a regression and have them fix it? They > can't just change things like this.
I did, informally. I was told that the atomics were to replace them. I have been bugging them about volatile ever since, given that some people would dearly like to eliminate volatile from the language. (I believe I am making good progress on preventing this, with a lot of help more recently.)
> > Me, I would feel better explicitly telling the compiler what I needed. > > It is all too easy for bugs to slip in otherwise, especially when the > > gcc guys are adding exciting new optimizations. > > GCC guys (as opposed to the language guys) should be far more amenable > to our needs, and I don't think they want to break the kernel any more > than we do.
Some are, some aren't. We should of course cherish the ones who would like to avoid breaking the kernel.
Thanx, Paul
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