ARC: Entry Handler tweaks: Optimize away redundant IRQ_DISABLE_SAVE

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>

diff --git a/arch/arc/include/asm/irqflags.h b/arch/arc/include/asm/irqflags.h
index d99f79bcf865a248ddb1c1dfa1eb35a58ae5f948..b68b53f458d1bc07f89b5b64c8f9fd9dc84ba323 100644 (file)
--- a/arch/arc/include/asm/irqflags.h
+++ b/arch/arc/include/asm/irqflags.h
@@ -157,13 +157,6 @@ 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 059ca94e3df8c8b6d86477421e71716f02bc026a..b908dde8a331c26a00a4912309af78cf643fc05b 100644 (file)
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -612,6 +612,9 @@ 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]
@@ -621,8 +624,6 @@ 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
 
@@ -635,12 +636,11 @@ 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]
 
        ; Restore REG File. In case multiple Events outstanding,
        ; use the same priorty as rtie: EXCPN, L2 IRQ, L1 IRQ, None