This is a note to let you know that I've just added the patch titled
ARM: 8128/1: abort: don't clear the exclusive monitors
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-8128-1-abort-don-t-clear-the-exclusive-monitors.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 85868313177700d20644263a782351262d2aff84 Mon Sep 17 00:00:00 2001
From: Mark Rutland <mark.rutland@xxxxxxx>
Date: Fri, 15 Aug 2014 12:11:49 +0100
Subject: ARM: 8128/1: abort: don't clear the exclusive monitors
From: Mark Rutland <mark.rutland@xxxxxxx>
commit 85868313177700d20644263a782351262d2aff84 upstream.
The ARMv6 and ARMv7 early abort handlers clear the exclusive monitors
upon entry to the kernel, but this is redundant:
- We clear the monitors on every exception return since commit
200b812d0084 ("Clear the exclusive monitor when returning from an
exception"), so this is not necessary to ensure the monitors are
cleared before returning from a fault handler.
- Any dummy STREX will target a temporary scratch area in memory, and
may succeed or fail without corrupting useful data. Its status value
will not be used.
- Any other STREX in the kernel must be preceded by an LDREX, which
will initialise the monitors consistently and will not depend on the
earlier state of the monitors.
Therefore we have no reason to care about the initial state of the
exclusive monitors when a data abort is taken, and clearing the monitors
prior to exception return (as we already do) is sufficient.
This patch removes the redundant clearing of the exclusive monitors from
the early abort handlers.
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/mm/abort-ev6.S | 6 ------
arch/arm/mm/abort-ev7.S | 6 ------
2 files changed, 12 deletions(-)
--- a/arch/arm/mm/abort-ev6.S
+++ b/arch/arm/mm/abort-ev6.S
@@ -17,12 +17,6 @@
*/
.align 5
ENTRY(v6_early_abort)
-#ifdef CONFIG_CPU_V6
- sub r1, sp, #4 @ Get unused stack location
- strex r0, r1, [r1] @ Clear the exclusive monitor
-#elif defined(CONFIG_CPU_32v6K)
- clrex
-#endif
mrc p15, 0, r1, c5, c0, 0 @ get FSR
mrc p15, 0, r0, c6, c0, 0 @ get FAR
/*
--- a/arch/arm/mm/abort-ev7.S
+++ b/arch/arm/mm/abort-ev7.S
@@ -13,12 +13,6 @@
*/
.align 5
ENTRY(v7_early_abort)
- /*
- * The effect of data aborts on on the exclusive access monitor are
- * UNPREDICTABLE. Do a CLREX to clear the state
- */
- clrex
-
mrc p15, 0, r1, c5, c0, 0 @ get FSR
mrc p15, 0, r0, c6, c0, 0 @ get FAR
Patches currently in stable-queue which might be from mark.rutland@xxxxxxx are
queue-3.10/arm-8133-1-use-irq_set_affinity-with-force-false-when-migrating-irqs.patch
queue-3.10/arm-8128-1-abort-don-t-clear-the-exclusive-monitors.patch
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