linux-kernel - [PATCH] Revert "local

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Message-ID: <478EB2CC.8000900@cn.fujitsu.com>
Date:	Thu, 17 Jan 2008 09:43:40 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	mathieu.desnoyers@...ymtl.ca, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] Revert "local_t Documentation update"

This reverts commit e1265205c0ee3919c3f2c750662630154c8faab2.

It's a duplicate commit of commit 74beb9db77930be476b267ec8518a642f39a04bf,
resulting in a duplicate section.

Signed-off-by: Li Zefan <lizf@...fujitsu.com>

---
 Documentation/local_ops.txt |   23 -----------------------
 1 files changed, 0 insertions(+), 23 deletions(-)

diff --git a/Documentation/local_ops.txt b/Documentation/local_ops.txt
index 1a45f11..4269a11 100644
--- a/Documentation/local_ops.txt
+++ b/Documentation/local_ops.txt
@@ -68,29 +68,6 @@ typedef struct { atomic_long_t a; } local_t;
   variable can be read when reading some _other_ cpu's variables.
 
 
-* Rules to follow when using local atomic operations
-
-- Variables touched by local ops must be per cpu variables.
-- _Only_ the CPU owner of these variables must write to them.
-- This CPU can use local ops from any context (process, irq, softirq, nmi, ...)
-  to update its local_t variables.
-- Preemption (or interrupts) must be disabled when using local ops in
-  process context to   make sure the process won't be migrated to a
-  different CPU between getting the per-cpu variable and doing the
-  actual local op.
-- When using local ops in interrupt context, no special care must be
-  taken on a mainline kernel, since they will run on the local CPU with
-  preemption already disabled. I suggest, however, to explicitly
-  disable preemption anyway to make sure it will still work correctly on
-  -rt kernels.
-- Reading the local cpu variable will provide the current copy of the
-  variable.
-- Reads of these variables can be done from any CPU, because updates to
-  "long", aligned, variables are always atomic. Since no memory
-  synchronization is done by the writer CPU, an outdated copy of the
-  variable can be read when reading some _other_ cpu's variables.
-
-
 * How to use local atomic operations
 
 #include <linux/percpu.h>
-- 
1.5.3.rc7

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