DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0C83720657
Date:   Thu, 1 Nov 2018 22:38:34 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc:     Eric Dumazet <eric.dumazet@gmail.com>,
        Trond Myklebust <trondmy@hammerspace.com>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "ralf@linux-mips.org" <ralf@linux-mips.org>,
        "jlayton@kernel.org" <jlayton@kernel.org>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "bfields@fieldses.org" <bfields@fieldses.org>,
        "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>,
        "linux@roeck-us.net" <linux@roeck-us.net>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "will.deacon@arm.com" <will.deacon@arm.com>,
        "boqun.feng@gmail.com" <boqun.feng@gmail.com>,
        "paul.burton@mips.com" <paul.burton@mips.com>,
        "anna.schumaker@netapp.com" <anna.schumaker@netapp.com>,
        "jhogan@kernel.org" <jhogan@kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "arnd@arndb.de" <arnd@arndb.de>,
        "paulus@samba.org" <paulus@samba.org>,
        "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
        "benh@kernel.crashing.org" <benh@kernel.crashing.org>,
        aryabinin@virtuozzo.com, dvyukov@google.com
Subject: Re: [RFC PATCH] lib: Introduce generic __cmpxchg_u64() and use it
 where needed
Message-ID: <20181101213834.GA3339@worktop.programming.kicks-ass.net>
References: <20181031233235.qbedw3pinxcuk7me@pburton-laptop>
 <4e2438a23d2edf03368950a72ec058d1d299c32e.camel@hammerspace.com>
 <20181101131846.biyilr2msonljmij@lakrids.cambridge.arm.com>
 <20181101145926.GE3178@hirez.programming.kicks-ass.net>
 <f38e272f7a96e983549e4281aa9fd02833a4277a.camel@hammerspace.com>
 <20181101163212.GF3159@hirez.programming.kicks-ass.net>
 <b0160f4b-b996-b0ee-405a-3d5f1866272e@gmail.com>
 <20181101171432.GH3178@hirez.programming.kicks-ass.net>
 <20181101172739.GA3196@hirez.programming.kicks-ass.net>
 <20181101202910.GB4170@linux.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20181101202910.GB4170@linux.ibm.com>
User-Agent: Mutt/1.5.22.1 (2013-10-16)
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

On Thu, Nov 01, 2018 at 01:29:10PM -0700, Paul E. McKenney wrote:
> On Thu, Nov 01, 2018 at 06:27:39PM +0100, Peter Zijlstra wrote:
> > On Thu, Nov 01, 2018 at 06:14:32PM +0100, Peter Zijlstra wrote:
> > > > This reminds me of this sooooo silly patch :/
> > > > 
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=adb03115f4590baa280ddc440a8eff08a6be0cb7
> > 
> > You'd probably want to write it like so; +- some ordering stuff, that
> > code didn't look like it really needs the memory barriers implied by
> > these, but I didn't look too hard.
> 
> The atomic_fetch_add() API would need to be propagated out to the other
> architectures, correct?

Like these commits I did like 2 years ago ? :-)

$ git log --oneline 6dc25876cdb1...1f51dee7ca74
6dc25876cdb1 locking/atomic, arch/xtensa: Implement atomic_fetch_{add,sub,and,or,xor}()
a8bcccaba162 locking/atomic, arch/x86: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
1af5de9af138 locking/atomic, arch/tile: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
3a1adb23a52c locking/atomic, arch/sparc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
7d9794e75237 locking/atomic, arch/sh: Implement atomic_fetch_{add,sub,and,or,xor}()
56fefbbc3f13 locking/atomic, arch/s390: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
a28cc7bbe8e3 locking/atomic, arch/powerpc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}{,_relaxed,_acquire,_release}()
e5857a6ed600 locking/atomic, arch/parisc: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
f8d638e28d7c locking/atomic, arch/mn10300: Implement atomic_fetch_{add,sub,and,or,xor}()
4edac529eb62 locking/atomic, arch/mips: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
e898eb27ffd8 locking/atomic, arch/metag: Implement atomic_fetch_{add,sub,and,or,xor}()
e39d88ea3ce4 locking/atomic, arch/m68k: Implement atomic_fetch_{add,sub,and,or,xor}()
f64937052303 locking/atomic, arch/m32r: Implement atomic_fetch_{add,sub,and,or,xor}()
cc102507fac7 locking/atomic, arch/ia64: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
4be7dd393515 locking/atomic, arch/hexagon: Implement atomic_fetch_{add,sub,and,or,xor}()
0c074cbc3309 locking/atomic, arch/h8300: Implement atomic_fetch_{add,sub,and,or,xor}()
d9c730281617 locking/atomic, arch/frv: Implement atomic{,64}_fetch_{add,sub,and,or,xor}()
e87fc0ec0705 locking/atomic, arch/blackfin: Implement atomic_fetch_{add,sub,and,or,xor}()
1a6eafacd481 locking/atomic, arch/avr32: Implement atomic_fetch_{add,sub,and,or,xor}()
2efe95fe6952 locking/atomic, arch/arm64: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}() for LSE instructions
6822a84dd4e3 locking/atomic, arch/arm64: Generate LSE non-return cases using common macros
e490f9b1d3b4 locking/atomic, arch/arm64: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()
6da068c1beba locking/atomic, arch/arm: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()
fbffe892e525 locking/atomic, arch/arc: Implement atomic_fetch_{add,sub,and,andnot,or,xor}()