Messages in this thread | | | Date | Mon, 20 Oct 2014 11:11:40 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH] futex: Ensure get_futex_key_refs() always implies a barrier |
| |
On Sat, 18 Oct 2014, Davidlohr Bueso wrote: > On Sat, 2014-10-18 at 13:50 -0700, Linus Torvalds wrote: > > On Sat, Oct 18, 2014 at 12:58 PM, Davidlohr Bueso <dave@stgolabs.net> wrote: > > > > > > And [get/put]_futex_keys() shouldn't even be called for private futexes. > > > The following patch had some very minor testing on a 60 core box last > > > night, but passes both Darren's and perf's tests. So I *think* this is > > > right, but lack of sleep and I overall just don't trust them futexes! > > > > Hmm. I don't see the advantage of making the code more complex in > > order to avoid the functions that are no-ops for the !fshared case? > > > > IOW, as far as I can tell, this patch doesn't actually really *change* > > anything. Am I missing something? > > Right, all we do is avoid a NOP, but I don't see how this patch makes > the code more complex. In fact, the whole idea is to make it easier to > read and makes the key referencing differences between shared and > private futexes crystal clear, hoping to mitigate future bugs.
I tend to disagree. The current code is symetric versus get/drop and you make it unsymetric by avoiding the drop call with a pointless extra conditional in all call sites.
I really had to look twice to figure out that the patch is correct, but I really cannot see any value and definitely have a hard time how this makes the code clearer and would prevent future bugs.
I rather keep it symetric and document the NOP property for private futexes in both get and drop.
Thanks,
tglx
| |