ARM: Avoid writing to control register on every exception
If we are not changing the control register value, avoid writing to it.
Writes to the control register can be very expensive, taking around a
hundred cycles or so.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index e52fe5a..6bb09d4 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -366,7 +366,7 @@
str r0, [sp, #S_OLD_R0] @ Save OLD_R0
#endif
zero_fp
- alignment_trap ip, __cr_alignment
+ alignment_trap r10, ip, __cr_alignment
enable_irq
ct_user_exit
get_thread_info tsk