> -----Original Message----- > From: Peter Zijlstra [mailto:peterz@xxxxxxxxxxxxx] > Sent: Friday, September 1, 2017 10:13 PM > To: Reshetova, Elena <elena.reshetova@xxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux- > fsdevel@xxxxxxxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; viro@xxxxxxxxxxxxxxxxxx; > tj@xxxxxxxxxx; mingo@xxxxxxxxxx; hannes@xxxxxxxxxxx; lizefan@xxxxxxxxxx; > acme@xxxxxxxxxx; alexander.shishkin@xxxxxxxxxxxxxxx; eparis@xxxxxxxxxx; > akpm@xxxxxxxxxxxxxxxxxxxx; arnd@xxxxxxxx; luto@xxxxxxxxxx; > keescook@xxxxxxxxxxxx; dvhart@xxxxxxxxxxxxx; ebiederm@xxxxxxxxxxxx > Subject: Re: [PATCH 14/15] futex: convert futex_pi_state.refcount to refcount_t > > On Fri, Sep 01, 2017 at 05:03:55PM +0000, Reshetova, Elena wrote: > > > On Fri, Sep 01, 2017 at 01:24:16PM +0000, Reshetova, Elena wrote: > > > > > > > > > On Fri, Sep 01, 2017 at 11:05:33AM +0000, Reshetova, Elena wrote: > > > > > > Actually on the second thought: does the above memory ordering > differences > > > > > > really apply when we have ARCH_HAS_REFCOUNT? To me it looks like the > way > > > > > > how it is currently implemented for x86 is the same way as it is for atomic > > > cases. > > > > > > > > > > Never look to x86 for memory ordering, its boring. > > > > > > > > > > And yes, for the ARM implementation it can certainly make a difference. > > > > > > > > So, yes, what I am trying to say is that it can really depend if you have > > > ARCH_HAS_REFCOUNT > > > > enabled or not and then also based on architecture. Thus I believe is also true > for > > > atomic: there > > > > might be differences when you use arch. dependent version of function or not. > > > > > > So the generic one in lib/refcount.c is already weaker on ARM, they > > > don't need to do a ARCH specific 'fast' implementation for the > > > difference to show up. > > > > But can they make "fast" implementation on ARM that would give stronger > memory guarantees? > > Whatever for? Well, maybe just by default when arch.-specific implementation is done. But I was just trying to speculate to understand. I will resend this one with new comment added. Still not sure if I need to resend the whole series with updated commits or break this up by individual patches further for the separate merges.
