From: Manfred Spraul <manfred@colorfullife.com>
To: paulmck@linux.vnet.ibm.com
Cc: benh@kernel.crashing.org, Ingo Molnar <mingo@elte.hu>,
Boqun Feng <boqun.feng@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
1vier1@web.de, Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH 2/4] barrier.h: Move smp_mb__after_unlock_lock to barrier.h
Date: Sun, 28 Aug 2016 20:00:43 +0200 [thread overview]
Message-ID: <ce8d6522-355b-a093-fa6a-f527f01186dc@colorfullife.com> (raw)
In-Reply-To: <20160828134321.GC19706@linux.vnet.ibm.com>
On 08/28/2016 03:43 PM, Paul E. McKenney wrote:
>
>> Without the smp_mb__after_unlock_lock(), other CPUs can observe the
>> write to d without seeing the write to a.
>>
>> Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
> With the upgraded commit log, I am OK with the patch below.
Done.
> However, others will probably want to see at least one use of
> smp_mb__after_unlock_lock() outside of RCU.
I would look at it from the other side:
There are at least half a dozen hardware/spinlock implementations that
must support rcu.
And for half a dozen implementations, a global header file makes sense,
regardless of the number of users.
With this in the global header file
> #ifndef complex_memory_barrier()
> #define complex_memory_barrier() always_safe_fallback()
> #endif
it is easier for the architectures to support rcu, ipc/sem and nf_conntrack.
Especially if everything is (as it is now) in <linux/spinlock.h>
--
Manfred
next prev parent reply other threads:[~2016-08-28 18:00 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-28 11:56 [PATCH 0/4] Clarify/standardize memory barriers for lock/unlock Manfred Spraul
2016-08-28 11:56 ` [PATCH 1/4] spinlock: Document memory barrier rules Manfred Spraul
2016-08-28 11:56 ` [PATCH 2/4] barrier.h: Move smp_mb__after_unlock_lock to barrier.h Manfred Spraul
2016-08-28 11:56 ` [PATCH 3/4] net/netfilter/nf_conntrack_core: update memory barriers Manfred Spraul
2016-08-28 11:56 ` [PATCH 4/4] qspinlock for x86: smp_mb__after_spin_lock() is free Manfred Spraul
2016-08-29 10:52 ` Peter Zijlstra
2016-08-29 10:51 ` [PATCH 3/4] net/netfilter/nf_conntrack_core: update memory barriers Peter Zijlstra
2016-08-28 13:43 ` [PATCH 2/4] barrier.h: Move smp_mb__after_unlock_lock to barrier.h Paul E. McKenney
2016-08-28 16:31 ` Manfred Spraul
2016-08-28 18:00 ` Manfred Spraul [this message]
2016-08-28 14:41 ` kbuild test robot
2016-08-28 17:43 ` [PATCH 2/4 v3] spinlock.h: Move smp_mb__after_unlock_lock to spinlock.h Manfred Spraul
2016-08-29 10:48 ` [PATCH 1/4] spinlock: Document memory barrier rules Peter Zijlstra
2016-08-29 12:54 ` Manfred Spraul
2016-08-29 13:44 ` Peter Zijlstra
2016-08-31 4:59 ` Manfred Spraul
2016-08-31 15:40 ` Peter Zijlstra
2016-08-31 16:40 ` Will Deacon
2016-08-31 18:32 ` Manfred Spraul
2016-09-01 8:44 ` Peter Zijlstra
2016-09-01 11:04 ` Manfred Spraul
2016-09-01 11:19 ` Will Deacon
2016-09-01 11:51 ` Peter Zijlstra
2016-09-01 14:05 ` Boqun Feng
2016-08-29 10:53 ` [PATCH 0/4] Clarify/standardize memory barriers for lock/unlock Peter Zijlstra
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