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From: Nicholas Piggin <npiggin@gmail.com>
To: Will Deacon <will@kernel.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>,
	Peter Zijlstra <peterz@infradead.org>,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 5/8] powerpc/64s: implement queued spinlocks and rwlocks
Date: Thu, 02 Jul 2020 20:25:43 +1000	[thread overview]
Message-ID: <1593685459.r2tfxtfdp6.astroid@bobo.none> (raw)
In-Reply-To: <20200702080219.GB16113@willie-the-truck>

Excerpts from Will Deacon's message of July 2, 2020 6:02 pm:
> On Thu, Jul 02, 2020 at 05:48:36PM +1000, Nicholas Piggin wrote:
>> diff --git a/arch/powerpc/include/asm/qspinlock.h b/arch/powerpc/include/asm/qspinlock.h
>> new file mode 100644
>> index 000000000000..f84da77b6bb7
>> --- /dev/null
>> +++ b/arch/powerpc/include/asm/qspinlock.h
>> @@ -0,0 +1,20 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef _ASM_POWERPC_QSPINLOCK_H
>> +#define _ASM_POWERPC_QSPINLOCK_H
>> +
>> +#include <asm-generic/qspinlock_types.h>
>> +
>> +#define _Q_PENDING_LOOPS	(1 << 9) /* not tuned */
>> +
>> +#define smp_mb__after_spinlock()   smp_mb()
>> +
>> +static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
>> +{
>> +	smp_mb();
>> +	return atomic_read(&lock->val);
>> +}
> 
> Why do you need the smp_mb() here?

A long and sad tale that ends here 51d7d5205d338

Should probably at least refer to that commit from here, since this one 
is not going to git blame back there. I'll add something.

Thanks,
Nick

  parent reply	other threads:[~2020-07-02 10:25 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
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 [this message]
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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