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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>
This commit is contained in:
Vineet Gupta 2013-07-09 17:06:40 +05:30
parent 37f3ac498c
commit fce16bc35a
2 changed files with 5 additions and 12 deletions
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7
arch/arc/include/asm/irqflags.h
View File

@ -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)

10
arch/arc/kernel/entry.S
View File

@ -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