ARC: Entry Handler tweaks: Optimize away redundant IRQ_DISABLE_SAVE

commit fce16bc35ae4a45634f3dc348d8d297a25c277cf upstream.

In the exception return path, for both U/K cases, intr are already
disabled (for various existing reasons). So when we drop down to
@restore_regs, we need not redo that.

There was subtle issue - when intr were NOT being disabled for
ret-to-kernel-but-no-preemption case - now fixed by moving the
IRQ_DISABLE further up in @resume_kernel_mode.

So what do we gain:

* Shaves off a few insn in return path.

* Eliminates the need for IRQ_DISABLE_SAVE assembler macro for ARCv2
  hence allows for entry code sharing.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 5 insertions, 12 deletions

diff --git a/arch/arc/include/asm/irqflags.h b/arch/arc/include/asm/irqflags.h
index eac071668201..c29d56587bf0 100644
--- a/arch/arc/include/asm/irqflags.h
+++ b/arch/arc/include/asm/irqflags.h
@@ -137,13 +137,6 @@ static inline void arch_unmask_irq(unsigned int irq)
         flag    \scratch
 .endm
 
-.macro IRQ_DISABLE_SAVE  scratch, save
-        lr      \scratch, [status32]
-        mov     \save, \scratch         /* Make a copy */
-        bic     \scratch, \scratch, (STATUS_E1_MASK | STATUS_E2_MASK)
-        flag    \scratch
-.endm
-
 .macro IRQ_ENABLE  scratch
         lr      \scratch, [status32]
         or      \scratch, \scratch, (STATUS_E1_MASK | STATUS_E2_MASK)
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index 922150e153ea..57f38333834b 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -653,6 +653,9 @@ resume_kernel_mode:
 
 #ifdef CONFIG_PREEMPT
 
+        ; This is a must for preempt_schedule_irq()
+        IRQ_DISABLE     r9
+
         ; Can't preempt if preemption disabled
         GET_CURR_THR_INFO_FROM_SP   r10
         ld  r8, [r10, THREAD_INFO_PREEMPT_COUNT]
@@ -662,8 +665,6 @@ resume_kernel_mode:
         ld  r9, [r10, THREAD_INFO_FLAGS]
         bbit0  r9, TIF_NEED_RESCHED, restore_regs
 
-        IRQ_DISABLE     r9
-
         ; Invoke PREEMPTION
         bl      preempt_schedule_irq
 
@@ -676,12 +677,11 @@ resume_kernel_mode:
 ;
 ; Restore the saved sys context (common exit-path for EXCPN/IRQ/Trap)
 ; IRQ shd definitely not happen between now and rtie
+; All 2 entry points to here already disable interrupts
 
 restore_regs :
 
-        ; Disable Interrupts while restoring reg-file back
-        ; XXX can this be optimised out
-        IRQ_DISABLE_SAVE    r9, r10     ;@r10 has prisitine (pre-disable) copy
+        lr      r10, [status32]
 
 #ifdef CONFIG_ARC_CURR_IN_REG
         ; Restore User R25