From: Nicholas Piggin <npiggin@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Anton Blanchard <anton@ozlabs.org>,
Boqun Feng <boqun.feng@gmail.com>,
kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
virtualization@lists.linux-foundation.org,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH 2/8] powerpc/pseries: use smp_rmb() in H_CONFER spin yield
Date: Thu, 02 Jul 2020 20:36:27 +1000 [thread overview]
Message-ID: <1593685552.uh4kepm08t.astroid@bobo.none> (raw)
In-Reply-To: <20200702082840.GC4781@hirez.programming.kicks-ass.net>
Excerpts from Peter Zijlstra's message of July 2, 2020 6:28 pm:
> On Thu, Jul 02, 2020 at 05:48:33PM +1000, Nicholas Piggin wrote:
>> There is no need for rmb(), this allows faster lwsync here.
>
> Since you determined this; I'm thinking you actually understand the
> ordering here. How about recording this understanding in a comment?
>
> Also, should the lock->slock load not use READ_ONCE() ?
Yeah, good point. Maybe I'll drop it from this series, doesn't really
belong I just saw the cleanup and didn't want to forget it.
We we just ordering the two loads in this function, and !SMP isn't a
concern (i.e., no issues of !SMP guest on SMP HV), but yeah fixing
the lack of comment is warranted, thanks.
Thanks,
Nick
next prev parent reply other threads:[~2020-07-02 10:36 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-02 7:48 [PATCH 0/8] powerpc: queued spinlocks and rwlocks Nicholas Piggin
2020-07-02 7:48 ` [PATCH 1/8] powerpc/powernv: must include hvcall.h to get PAPR defines Nicholas Piggin
2020-07-02 7:48 ` Nicholas Piggin
2020-07-02 7:48 ` [PATCH 2/8] powerpc/pseries: use smp_rmb() in H_CONFER spin yield Nicholas Piggin
2020-07-02 7:48 ` Nicholas Piggin
2020-07-02 8:28 ` Peter Zijlstra
2020-07-02 8:28 ` Peter Zijlstra
2020-07-02 10:36 ` Nicholas Piggin [this message]
2020-07-02 10:36 ` Nicholas Piggin
2020-07-02 7:48 ` [PATCH 3/8] powerpc/pseries: move some PAPR paravirt functions to their own file Nicholas Piggin
2020-07-02 7:48 ` [PATCH 4/8] powerpc: move spinlock implementation to simple_spinlock Nicholas Piggin
2020-07-02 7:48 ` Nicholas Piggin
2020-07-02 7:48 ` [PATCH 5/8] powerpc/64s: implement queued spinlocks and rwlocks Nicholas Piggin
2020-07-02 8:02 ` Will Deacon
2020-07-02 8:02 ` Will Deacon
2020-07-02 10:25 ` Nicholas Piggin
2020-07-02 10:25 ` Nicholas Piggin
2020-07-02 10:35 ` Will Deacon
2020-07-02 10:47 ` Nicholas Piggin
2020-07-02 10:47 ` Nicholas Piggin
2020-07-02 10:48 ` Will Deacon
2020-07-02 10:48 ` Will Deacon
2020-07-03 10:52 ` Michael Ellerman
2020-07-03 10:52 ` Michael Ellerman
2020-07-02 7:48 ` [PATCH 6/8] powerpc/pseries: implement paravirt qspinlocks for SPLPAR Nicholas Piggin
2020-07-02 21:01 ` Waiman Long
2020-07-02 7:48 ` [PATCH 7/8] powerpc/qspinlock: optimised atomic_try_cmpxchg_lock that adds the lock hint Nicholas Piggin
2020-07-02 7:48 ` Nicholas Piggin
2020-07-02 7:48 ` [PATCH 8/8] powerpc/64s: remove paravirt from simple spinlocks (RFC only) Nicholas Piggin
2020-07-02 7:48 ` Nicholas Piggin
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