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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- synchronization is done by the writer CPU, an outdated copy of the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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