linux-kernel - [PATCH 0/4 V4] Clarify/standardize memory barriers for lock/unlock

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Message-Id: <1472477669-27508-1-git-send-email-manfred@colorfullife.com>
Date:   Mon, 29 Aug 2016 15:34:25 +0200
From:   Manfred Spraul <manfred@...orfullife.com>
To:     benh@...nel.crashing.org, paulmck@...ux.vnet.ibm.com,
        Ingo Molnar <mingo@...e.hu>, Boqun Feng <boqun.feng@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, 1vier1@....de,
        Davidlohr Bueso <dave@...olabs.net>,
        Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH 0/4 V4] Clarify/standardize memory barriers for lock/unlock

Hi,

V4: Docu/comment improvements, remove unnecessary barrier for x86.
V3: Bugfix for arm64
V2: Include updated documentation for rcutree patch

As discussed before:
If a high-scalability locking scheme is built with multiple
spinlocks, then often additional memory barriers are required.

The documentation was not as clear as possible, and memory
barriers were missing / superfluous in the implementation.

Patch 1: Documentation, define one standard barrier, update ipc/sem.c
Patch 2: Update rcutree
Patch 3: Update nf_conntrack
Patch 4: Update for qspinlock: smp_mb__after_spin_lock is free.

Patch 3 is larger than required, it rewrites the conntrack logic
with the code from ipc/sem.c. I think the new code is simpler
and more realtime-friendly.

Please review!

@Andrew: The patches are relative to mmots.
Could you include them in your tree, with the target of including in
linux-next?

--
	Manfred