Commit 8630bac3 authored by Mark Rutland's avatar Mark Rutland Committed by Ben Hutchings

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

commit 85868313 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
    200b812d ("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: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent b23ea023
......@@ -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
/*
......
......@@ -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
......
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