Commit fce16bc3 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

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: default avatarVineet Gupta <vgupta@synopsys.com>
parent 37f3ac49

arch/arc/include/asm/irqflags.h

+0 −7
Original line number Diff line number Diff line
@@ -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)

arch/arc/kernel/entry.S

+5 −5
Original line number Diff line number Diff line
@@ -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

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