ARM: 8128/1: abort: don't clear the exclusive monitors

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@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/mm/abort-ev6.S b/arch/arm/mm/abort-ev6.S
index 3815a8262af070b98f33d61ac31908961ee06eb2..8c48c5c22a331aac8f547335d6990c598457ef0b 100644 (file)
--- 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
 /*

diff --git a/arch/arm/mm/abort-ev7.S b/arch/arm/mm/abort-ev7.S
index 703375277ba6d3dcdae7f93404d2d19e531aad68..4812ad054214572ba6e7198247e2c190e469897d 100644 (file)
--- 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