From: Peter Zijlstra <peterz@infradead•org>
To: Will Deacon <will.deacon@arm•com>
Cc: "Paul E. McKenney" <paulmck@linux•vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail•com>,
"linux-kernel@vger•kernel.org" <linux-kernel@vger•kernel.org>,
"linuxppc-dev@lists•ozlabs.org" <linuxppc-dev@lists•ozlabs.org>,
Ingo Molnar <mingo@kernel•org>,
Benjamin Herrenschmidt <benh@kernel•crashing.org>,
Paul Mackerras <paulus@samba•org>,
Michael Ellerman <mpe@ellerman•id.au>,
Thomas Gleixner <tglx@linutronix•de>,
Waiman Long <waiman.long@hp•com>
Subject: Re: [RFC 3/5] powerpc: atomic: implement atomic{,64}_{add,sub}_return_* variants
Date: Mon, 14 Sep 2015 13:35:20 +0200 [thread overview]
Message-ID: <20150914113520.GP18489@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150911124507.GB16833@arm.com>
Sorry for being tardy, I had a wee spell of feeling horrible and then I
procrastinated longer than I should have.
On Fri, Sep 11, 2015 at 01:45:07PM +0100, Will Deacon wrote:
> Peter, any thoughts? I'm not au fait with the x86 memory model, but what
> Paul's saying is worrying.
Right, so Paul is right -- and I completely forgot (I used to know about
that).
So all the TSO archs (SPARC-TSO, x86 (!OOSTORE) and s390) can do
smp_load_acquire()/smp_store_release() with just barrier(), and while:
smp_store_release(&x);
smp_load_acquire(&x);
will provide full order by means of the address dependency,
smp_store_release(&x);
smp_load_acquire(&y);
will not. Because the one reorder TSO allows is exactly that one.
> Peter -- if the above reordering can happen on x86, then moving away
> from RCpc is going to be less popular than I hoped...
Sadly yes.. We could of course try and split LOCK from ACQUIRE again,
but I'm not sure that's going to help anything except confusion.
next prev parent reply other threads:[~2015-09-14 11:35 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-28 2:48 [RFC 0/5] atomics: powerpc: implement relaxed/acquire/release variants of some atomics Boqun Feng
2015-08-28 2:48 ` [RFC 1/5] atomics: add test for atomic operations with _relaxed variants Boqun Feng
2015-08-28 2:48 ` [RFC 2/5] atomics: introduce arch_atomic_op_{acquire, release, fence} helpers Boqun Feng
2015-08-28 11:36 ` [RFC 2/5] atomics: introduce arch_atomic_op_{acquire,release,fence} helpers Peter Zijlstra
2015-08-28 11:50 ` Boqun Feng
2015-08-28 2:48 ` [RFC 3/5] powerpc: atomic: implement atomic{, 64}_{add, sub}_return_* variants Boqun Feng
2015-08-28 10:48 ` [RFC 3/5] powerpc: atomic: implement atomic{,64}_{add,sub}_return_* variants Peter Zijlstra
2015-08-28 12:06 ` Boqun Feng
2015-08-28 14:16 ` Boqun Feng
2015-08-28 15:39 ` Peter Zijlstra
2015-08-28 16:59 ` Boqun Feng
2015-09-01 19:00 ` Will Deacon
2015-09-01 21:45 ` Paul E. McKenney
2015-09-02 9:59 ` Will Deacon
2015-09-02 10:49 ` Paul E. McKenney
2015-09-02 15:23 ` Pranith Kumar
2015-09-02 15:36 ` [RFC 3/5] powerpc: atomic: implement atomic{, 64}_{add, sub}_return_* variants Pranith Kumar
2015-09-03 10:31 ` [RFC 3/5] powerpc: atomic: implement atomic{,64}_{add,sub}_return_* variants Will Deacon
2015-09-11 12:45 ` Will Deacon
2015-09-11 17:09 ` Paul E. McKenney
2015-09-14 11:35 ` Peter Zijlstra [this message]
2015-09-14 12:01 ` Peter Zijlstra
2015-09-14 12:11 ` Peter Zijlstra
2015-09-14 15:38 ` Will Deacon
2015-09-14 16:26 ` Paul E. McKenney
2015-08-28 2:48 ` [RFC 4/5] powerpc: atomic: implement xchg_* and atomic{, 64}_xchg_* variants Boqun Feng
2015-08-28 2:48 ` [RFC 5/5] powerpc: atomic: implement cmpxchg{, 64}_* and atomic{, 64}_cmpxchg_* variants Boqun Feng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150914113520.GP18489@twins.programming.kicks-ass.net \
--to=peterz@infradead$(echo .)org \
--cc=benh@kernel$(echo .)crashing.org \
--cc=boqun.feng@gmail$(echo .)com \
--cc=linux-kernel@vger$(echo .)kernel.org \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=mingo@kernel$(echo .)org \
--cc=mpe@ellerman$(echo .)id.au \
--cc=paulmck@linux$(echo .)vnet.ibm.com \
--cc=paulus@samba$(echo .)org \
--cc=tglx@linutronix$(echo .)de \
--cc=waiman.long@hp$(echo .)com \
--cc=will.deacon@arm$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox